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Tag Archives: strokes gained

Predicting Putting Performance by Distance

Mark Broadie’s research of the Shot Link data established a clear relationship between putt distance and % of putts made. PGA Tour pros make a very high percentage of their close putts, but only about half of their putts around 10 feet and only around one in six around 20 feet. Pros hole very few (~5%) of their longest efforts from 25 feet and beyond. That data on % of putts made for each distance now forms the backbone of the PGA Tour’s Strokes Gained Putting statistic where players are credited and debited for making or missing every putt from every distance. Over a single season Strokes Gained Putting is often an unreliable indicator of putting performance, particularly at the extremes and also for players who have putted much worse or much better than in previous seasons.

Putting performance is polluted by randomness; Tour players just don’t attempt enough putts over the course of the season to get an accurate picture of their underlying putting ability. However, to make accurate projections of putting ability, you need to know whether Graeme McDowell’s 0.9 putts gained this season represents more talent or more luck. I’ve broken down putting performance into four different distance buckets from the PGA Tour data: putts inside 5 feet, 5-15 footers, 15-25 footers, and putts outside 25 feet. The results show that putting performance is far more predictable and consistent at the short distances. Long putting is so noisy that it’s difficult to say anyone gains much of an advantage from their long putting over the long-term.

Inside 5 Feet:

These putts are almost always converted (average 96%). The spread in performance between 2011-14 was 93% to 99%. The spread in expected performance derived from weighting the previous four seasons is 94.3% to 97.8%. This indicates that we should expect every regular Tour player’s true talent from inside 5 feet to fall somewhere inside that 3.5% range. Based on an average of over 900 putts attempted inside 5 feet over a season, we should expect every regular Tour player’s talent in terms of putts gained or lost to fall between +0.2/round and -0.3/round.

The graph below shows the correlation between a three year average (2011-13) and 2014 performance for all players with qualifying rounds in all four seasons. The correlation (R=0.56) between prior performance and 2014 performance is strongest in this distance range.

inside5feet

5-15 foot Putts:

This length is either short birdie putts or par putts after a scrambling shot that are converted approximately half the time. The spread in performance between 2011-14 was 36% to 54%. The spread in expected performance derived from weighting the previous four seasons is 40% to 52%. Based on around 450 putts attempted from 5-15 feet over a season, we should expect every regular Tour player’s talent in terms of putts gained or lost to fall between +0.4/round and and -0.5/round. Compare that to the best putters on Tour gaining about 0.75 putts/round.

The correlation between three year average and 2014 performance is below. The correlation (R=0.53) is similar to that for the short <5 foot putts.

5-15 footers

15-25 foot Putts:

These length are normally longer birdies putts and are converted about 16% of the time. The spread in performance between 2011-14 was 8% to 26%. The spread in expected performance derived from weighting the previous four seasons is 12% to 20%. Based on around 225 putts attempted from 15-25 feet over a season, we should expect every regular Tour player’s talent in terms of putts gained or lost to fall between +0.15/round and and -0.15/round. There’s much less at stake from this range than the previous two, just because so few putts are attempted from 15-25 feet.

The correlation between three year average and 2014 performance is below. There’s not much of a relationship (R=0.28), showing that putting performance from this range is much more affected by random chance over a full season than the shorter length putts.

15-25 footers

Putts outside 25 feet:

These length are the longest birdie putts, often really lag putts just to get it close for par. The spread in performance between 2011-14 was 2% to 13%. The spread in expected performance derived from weighting the previous four seasons is 4% to 9%. Based on around 300 putts attempted from beyond 25 feet over a season, we should expect every regular Tour player’s talent in terms of putts gained or lost to fall between +0.1/round and and -0.1/round. Again, there’s very little difference in expected performance from this distance. Even the very best long putter on Tour will gain little from these putts – over the long term.

The correlation between three year average and 2014 performance is below. There’s almost no relationship (R=0.10), which means it’s almost impossible to predict how well a player will putt on these long putts. The top ten long putters from 2011-13 average hitting 7.6% of their putts (versus 5.5% average). They only hit 6.7% of their putts in 2014 – a regression of almost 50% to the mean.

outside25ft

The Big Picture:

This graph shows performance in all four ranges. The longer putts show little relationship to future performance, while the shorter putts do show a more consistent relationship. This means that players who gained a lot of putts last season based off their longer putts will start making putts at a lower rate, while those who gained a lot of putts based on shorter putts are better bets to retain that putting ability.

bigpicture

Most Improved Putters from 5-15 feet in 2014:

1. Graeme McDowell

2. Charley Hoffman

3. Billy Horschel

4. Justin Leonard

5. Michael Thompson

These guys have a better chance of retaining their putting performance into 2015.

Most Improved Putters from > 25 feet in 2014:

1. Rory McIlroy

2. Y.E. Yang

3. David Toms

4. Brendan Steele

5. Brian Gay

These guys look likely to regress in terms of putting performance, especially McIlroy who performed to career average on all other putts, but hit 8% more of his long putts – gaining almost a third of a putt per round over his career average.

Measuring the Signal in First Round Performance

After the 1st Round of the Deutsche Bank Championship a month ago, Keegan Bradley sat two strokes off the lead. Playing in front of the home fans, Bradley fired a six under 65 fueled by great putting (4.2 strokes gained) and a solid long game (2.3 strokes gained on tee shots and approach shots). At that point he looked in great shape keep it going and capture his first win of the season. However, he came out the next three rounds and shot 71-69-71 to finish T16. The culprit wasn’t his long game either; he gained 1.6 strokes on the field per round in the second, third, and fourth rounds, good enough to finish in the top ten for the event in strokes gained off tee shots and approach shots. No, it was the putter that let him down. After being hot in the opening round, he actually lost 0.4 strokes per round from his putting.

My question is: how common is Bradley’s experience? When golfers come out in the 1st round and play/putt very well, how often do they keep playing/putting well? What about when they come out hitting the tee shots and approach shots well? Does that carry over to the next day? Many around the game act like one round of performance is really meaningful (just look at everyone who advocated for playing Jordan Spieth and Patrick Reed after their Friday morning 5&4 win at the Ryder Cup), but does first round performance tell us anything about how a player will perform in the following round?

Looking at Putting:

I gathered round by round Strokes Gained Putting data from the twelve most recent PGA Tour tournaments (Travelers Championship through the Tour Championship). First, I checked how 1st round putting performance predicted 2nd round putting performance. That’s the first graph below, and the results show how player putted in the 1st round hardly sheds any light on how they will putt in the 2nd round (R^2 of 0.001). In fact, someone who putted as well as Keegan Bradley did in the above mentioned round would be predicted only to putt 0.2 strokes above average the following round.

rd1SGP v rd2SGP

Next I generated prior expectations of Strokes Gained Putting performance from the past several years of data. I’ve shown before that putting performance isn’t very consistent season-to-season, so I’m using performance from 2011 to 2014 to generate the prior. The below graph shows how well the prior expectation predicted 2nd round putting. The results still were not highly predictive – R^2 of 0.01 (performance round to round is highly variable in golf) – but the regression line produced tracks pretty closely with results. Players predicted by the prior to putt well generally putted well and those predicted to putt poorly generally putted poorly.

priorSGP v Rd2SGP

Finally, I tied both pieces of information together. The prior estimate proved way more predictive than just 1st round performance, but does 1st round performance have any information to add? I set-up a linear regression with the prior estimate as x1 and the 1st round performance as x2. The results indicated 1st round putting performance provides no extra information to predict 2nd round putting performance (the coefficient was indistinguishable from zero). If you have a good guess of how well a player will putt, you can safely ignore first round putting performance.

Looking at Long Game Performance:

The long game is tee shots and approach shots (drivers/woods/irons essentially). I gathered long game performance data from the same twelve PGA Tour tournaments for the first and second rounds. I then ran the exact studies as above just substituting long game data for putting data. The correlation between 1st round long game performance and 2nd round long game performance was higher than with putting, but still didn’t contain a lot of information (R^2 of 0.03). If a player plays four strokes above field average in long game strokes gained, they’re expected to play 0.6 strokes better in the long game in the 2nd round.

rd1LONG vs rd2LONG

There was also a higher correlation between my prior estimate for long game ability and 2nd round long game performance (R^2 = 0.10). Again though, the regression line tracks closely with the results. Top ten long game players (around +1.2 strokes or above) generally performed to that level in the 2nd round.

priorLONG vs. rd2LONG

Tying both pieces together indicated that there is a small amount of signal in 1st round long game performance. Combining the prior estimate with 1st round performance slightly increases the fit of the model. The regression equation suggests that you should weight your prior estimate at twelve times the strength of first round performance. This indicates that someone who is PGA Tour average in long game shots, but produces an elite round of 4.0 long game strokes gained, should be expected to play about 0.3 strokes above average in long game shots. That seems like a small difference, but it’s enough of a shift in talent to move a player from around 50th best in the world to about 30th best in the world.

The Takeaway:

Based on these results, it looks like 1. a single round of performance is much less predictive than an estimate built on past-performance and 2. the small amount of signal contained in single rounds is from performance on tee shots and approach shots. Putting results from one round provide no more information than was available before the round. On the other hand, golfers who play particularly well on tee shots and approach shots in a round should perform slightly better than expected the following round.

 

The Barclays Round 1 Recap

Bo Van Pelt (-6) leads eight others including former FedEx Champ Jim Furyk after the first round at The Barclays. The main story in golf the last month has been the dominance of Rory McIlroy (three straight wins) and Rickie Fowler (two 2nds in majors), and what their success at a young age means to the future of golf. Rory struggled across the board Thursday – breaking a streak of fourteen straight above-average rounds dating back to early July – while Rickie delivered another solid round to end up three off the lead. Most notable from Thursday was the continued great play of Jim Furyk; he’s racked up three top tens and a T15 in the last month behind great iron play and a hot putter.

The Course:

Ridgewood was set-up at an average length Thursday and yielded fairly normal course stats in terms of accuracy (64%), GIR (67%), and scoring (70.8 on a par of 71). Where it’s really difficult is from the rough. It was in the upper tier of PGA Tour courses in terms of difficulty. The par 5s also play mostly as three shot holes; the pros only went for the green in two 17% of the time (average of 50%) and hit the green in two 2% of the time (average 14%).

Drivable Par 4 5th:

The 5th is a drivable par 4, playing 283 yards on Thursday, that is one of the best examples of a drivable par 4 all season. If you take a look below you’ll see the elevated green is narrow and tiny, measuring 9 yards wide and only 2200 square feet (microscopic by PGA Tour standards). The green is surrounded by bunkers to dissuade some from attacking it off the tee; lay-ups are made to around 85 yards. Driving the green requires a carry of around 270 yards, 40 feet uphill, and is best done with a right-handed fade. Just over half the field went for the green off the tee, scoring about 0.1 stroke better than those who laid-up.

Because of the carry required, none of the shortest hitters who went for the green hit it or made birdie. Because there isn’t a ton of difference between the expected values of each strategy, the shorter hitters and anyone who’s really good with a wedge from 100 yards in should probably lay-up. Anyone with average or better distance should absolutely take-on the green though. Average or longer hitters who went for the green scored at 3.60, everyone else at 3.91. The real pay-off isn’t really being close to the green – a 25 yard bunker shot isn’t much easier than a 75 yarder from the fairway – it’s instead in actually hitting the green. All five who hit the green made birdie, which is expected when the longest possible putt you can face is 50 feet. You can see the distribution by score below.

#5ridgewood1stround

What’s Ahead for Rory:

With Rory’s run of success every poor round is apt to be magnified beyond proportions. Even great players play poorly some days. Rory’s expected to have a round as bad as Thursday’s only around once every 25 rounds, so this is likely as poor as we’re apt to see him play for awhile. What’s important isn’t really this round, but how he’s had success so far this year. Rory emerged as a star and won his first two majors in 2011 and 2012 while being wholly dependent on his driver/irons for success. He was the best in the world on those long shots in 2011-12, while his putting was average or a bit worse. Last year, his driving was wild and he lost a lot his long game that had made him great. This year, the driving is as good as ever and his irons are great, but what’s really different is his success with the putter. He’s jumped to 21st on Tour in putting, gaining about half a stroke from putting compared to the last few seasons. Over this latest run of wins his putter has been nuclear hot (+1.20 strokes vs. the field). That’s been enough to take him from one of a group of 3-4 elite players to the best in the world.

The problem is putting is hugely random. Players putt well above their talent level for months and then regress. Up until July, McIlroy had putted at +0.16 strokes gained for the season and slightly below average for his career. Since then he’s at +1.20 strokes gained. This post deals with the small sample randomness involved with putting; nothing McIlroy is doing on the greens indicates to me that he’s going to sustain the level of putting that won him two majors in the last month. When his putting returns to his career norms, he’ll still be the best player in the world, but as more of a 1A to Sergio, Adam Scott, and Justin Rose than the next Tiger/Jack that he’s been made out as the last few weeks. His long game (driving/approach shots) is the best in the world largely because he’s in another universe off the tee. When Tiger was dominant for a decade he combined the best long game in the world with top ten putting; nothing Rory has done shows that he’s capable of putting that well for the long haul.

mcilroySG11-14McIlroy’s Strokes Gained per Shot Link tournament since 2011. His putting surge in the last few months is obvious.

Rickie Fowler’s Putting:

Much of the previous section applies to Rickie Fowler as well. Fowler took on a highly publicized swing change with Butch Harmon at the beginning of the season which left his game a mess for months, but which looks great now. His tee to green game has been the best of his career the last two months – a testament to the work he put in with Butch earlier this season. However, what’s really fueled him to four straight top tens in major tournaments has been a ridiculous run of putting. He’s putting about a stroke better per round than he ever has since June. He’s a solid putter in his career, but he’ll look mortal when this hot streak ends.

fowlerSGRickie Fowler’s Performance in Strokes relative to the field (positive is better)

Today’s round is a good example; his very good long game was erratic and his short game was awful. What saved him was gaining 4.5 putts on the field including two 13′ and two 11′ putts to save par after missing greens. You look real good when you hit all four of those, but most of the time you hit only 1-2. That’s why Rickie’s sitting on a -3 instead of a -1.

Shot of the Day:

The PGA Tour chose Bo Van Pelt’s eagle chip-in on #17. You can see on the video that it was a long chip (48 feet), but from right off the green. It ranked 6th among non-putts in terms of strokes gained (+1.3 strokes).

My highest ranked shot was Chris Stroud’s 20 yard hole-out from the bunker on the 7th (+1.5 strokes), for which there is no video available. Andrew Svoboda’s drive onto the the green 30 feet away at the drivable 5th hole was the best tee or approach shot of the day (+1.2 strokes), setting up a two putt birdie.

How He Won: Brendon Todd at the Byron Nelson

Some quick stats from Brendon Todd’s victory this weekend:

On average, PGA Tour winners putt much better than normal on the weeks they win. Since the start of 2013, the winners putted 1.3 strokes/round better than normal. Brendon Todd putted 1.9 strokes/round better than he normally does, a massive 2.4 strokes/round gained on the field. That putting performance would rank 7th among 2013-14 winners behind Bill Haas (AT&T National), Tiger Woods (Arnold Palmer), Russell Henley (Sony), Jimmy Walker (Frys), Webb Simpson (Las Vegas), and Matt Jones (Houston).

On average, PGA Tour winners also play tee to green much better than normal. Since the start of 2013, the winners played 1.8 strokes/round better tee to green than normal. Brendon Todd is basically average tee to green normally and he played in 1.65 fewer strokes/round. That over-performance is fairly low for winners; since 2013, only Tiger Woods (WGC-Cadillac), Jonas Blixt (Greenbrier), Jimmy Walker (Frys), and Matt Jones (Houston) were worse tee to green. Todd joins Blixt, Zach Johnson (Hyundai T of C), and Travelers champ Ken Duke as the only two winners in 2013 not to hit more greens than the field. Todd hit only 60% of his greens compared to 62% by the field, as well as driving it six yards shorter than the field off the tee. This was not a tournament won with the driver, woods, or long irons.

His tee to green performance was almost entirely a result of his scrambling. I don’t have shot-by-shot scrambling data for the other 2013-14 winners, but Todd gained 6.1 of 6.5 tee to green strokes from his short game – including three hole outs worth over a stroke a piece. I suspect that is abnormal. Some level of scrambling over-performance is a necessity to win on Tour, but I’m referring only to short game strokes. Gaining over six strokes in that manner seems extremely high.

It’s important to note that short term performance in putting and scrambling is much more random than other tee to green play. Based on that, it’s unsurprising that PGA Tour winners over-perform by so much in their putting. In fact since the start of 2013 only Steven Bowditch (Texas) has won a tournament putting worse than the field; only four others have gained fewer than two strokes on the field through putting over the weekend.

Review of Every Shot Counts – Mark Broadie

Mark Broadie’s Every Shot Counts: Using the Revolutionary Strokes Gained Approach to Improve Your Golf Performance and Strategy (2014) is the long-awaited full-length explanation of his strokes gained research. Broadie had published numerous academic papers discussing his strokes gained method and the PGA Tour has been showing the Strokes Gained Putting stat for a few years, so much of this material is merely rehashed from articles others have written or from his 2011 paper “Assessing Golfer Performance on the PGA Tour“. It’s well known that Broadie’s research has disproved putting as the most important part of the game and has elevated the long-game (driving and long approach shots) in its place, but where this book shines is in its lessons for applying this new knowledge to actually playing the game, whether you’re a pro, advising a pro, or an amateur.

Broadie spends the first six chapters basically explaining the strokes gained method. He covers why putting is overrated, why traditional putting statistics are worthless, and how the strokes gained method works. He then introduces strokes gained for the tee-to-green game. Broadie establishes that why the long-game is so important in separating elite pros from average pros, average pros from good amateurs, and good amateurs from 90 handicappers; in the process he shows why Tiger dominated golf so much in the last decade (he was good at everything, but the #GOAT at playing long approach shots). This part of the book is worthwhile for the more in-depth exploration of the strokes gained method, but if you’ve read his academic work feel free to skim it for the handful of insights.

Essentially, Broadie’s work is about how fractional strokes are so important in separating pro golfers. The best and worst golfers in a PGA Tour tournament are separated by 2.5 strokes/round. Most of that separation is manifested in things like hitting an extra green each round, driving the ball five yards further, leaving your shots from the sand a foot closer, and/or hitting a single approach shot within birdie range. His research argues for a strategy that considers all possible shots and outcomes of those shots, and selects the highest expected value play. In this recent interview, Broadie says that most golfers don’t play aggressively enough; they leave putts short of the hole, lay-up on par 5s, and hit woods/hybrids off the tee when they’d be better served hitting driver. Central to his work is the idea that being much closer to the hole is worth playing out of the rough/fairway bunker.

Broadie finally explores new ground the final three chapters, laying out how this new knowledge should be applied to all aspects of the game. In Chapter Seven, Broadie explores what the strokes gained analysis means for putting and how to figure out how aggressive to be on long putts. He explains that many PGA Tour golfers aren’t aggressive enough with their putting; they often purposefully don’t hit putts with enough force to get to the hole, ensuring that they miss the putt. There’s a lot of work in this chapter figuring out optimal aim points from different locations on the green; very interesting work for amateurs who are looking to improve their strategy on the green.

In Chapter Eight he explores how to optimize your long game to shave wasted strokes. Much of the chapter is spent on figuring out the proper way to target drives to ensure you miss the dangerous hazards (water, out of bounds), even if you are forced to play less from the fairway. This section would be very useful for amateurs who often find themselves wasting strokes off the tee by not being cognizant of where the dangerous areas of the course are. Broadie also spends this chapter detailing why lay-ups are typically a minus EV play – particularly notable this week after the way Patrick Reed laid-up so poorly down the stretch at Doral.

Chapter Nine is a detailed look at numerous different practice methods that use the ideas behind valuing each stroke and playing the highest EV game. I mainly skimmed these, but amateurs might find the lessons/games useful for improving their play.

I did pick up a few interesting lessons:

1. It’s well established that those who hit for more distance off the tee usually hit fewer than average fairways, but Broadie has actually found that longer players have a smaller degree of error in terms of how off-line they hit their shots. In fact, the only reason many long hitters hit fewer fairways is because when they do hit a shot with a larger than average degree of error, the increased distance cause it to fly/roll further off-line – into bunkers and the rough. Driving is basically a geometry problem where a smaller angle and larger hypotenuse can produce a larger miss.

2. Broadie introduces the concept of “median leave” in Chapter Five. The PGA Tour publishes stats showing the average proximity to the hole from approach shots, the rough, green-side bunkers, etc. However, Broadie argues we should use the median proximity instead because it’s not distorted by larger misses (like when you fly the green and leave it 50 yards from the hole). Median leave is simply the distance remaining to the pin after the shot divided by the distance to the pin before the shot. So a 150 yard approach to 18 feet would be a median leave of 4%. The best approach shot players have a median leave of 5.5% – equivalent to hitting it a median proximity of 29 feet from the average PGA approach shot (175 yards).

3. When discussing optimal driving strategy he explains the idea of “shot pattern”. Your shot pattern is all the possible results of each type of shot, considering the distance you can hit with a club, the degree of accuracy, and any spin/fade/draw/slice/etc. you can play. Golf is a game where each swing is essentially slightly random – a golfer might swing perfectly, contact the ball perfectly, judge the wind perfectly, and get the right amount of spin when he lands it on the green, but more likely his swing will be slightly off or he’ll mishit it slightly or the wind will push it offline a bit, or it will roll-out when it hits the green. The optimal golfer will know their 95% confidence interval for a 125 yard wedge shot, his average degree of miss when he hits driver, and all the possible results of an approach shot if the greens are firmer than expected. The optimal golfer will play their shots with all that understanding and avoid playing shots that are excessively conservative or needlessly risky.

All in all, it’s a worthwhile book if you’re interested in applying Broadie’s research to your golf game or at least interested in how a pro might apply it to how they work around a golf course. Broadie has plenty of evidence of some of the elite golf instructors already using this kind of stuff to help their clients excel. On the other hand if you’re just interested in the research itself, reading the literature I linked above is sufficient. His initial six chapters don’t provide a substantial amount of expansion on his earlier papers.

How He Won: Kevin Stadler (Phoenix Open)

Most posts here are focused on the macro-level of how to predict performance. That’s my main interest and the most valuable research in terms of the big picture of golf analytics. However, occasionally it’s nice to delve into individual performances and look at how golfers win each week. This week, Kevin Stadler finally broke through and won his first PGA tournament at the Phoenix Open. Stadler’s performance over the 2008-Present period has been approximately that of the 150th best player in the world, though he’s played much better in the last two seasons. Guys like that (even with famous fathers) rarely play their way into a 4th round lead at a tournament, so it’s nice to see Stadler break-through.

How he won is interesting though. This post detailed some quick stats on how PGA tournament winners putted during the 2013 season. The average winner gained ~1.5 strokes on the field each round due to putting. The winner normally gains 14-15 strokes on the field during the week, so putting normally accounts for at least 40% of the winner’s strokes gained on the field. However, Stadler totaled just short of 2 strokes gained due to putting for the entire week, while he finished 14.6 strokes better than the field in total. I don’t have detailed figures for other tournaments at my fingertips, but he must’ve far outperformed the field in all other phases of the game to finish so highly while putting (comparatively) poorly among PGA tournament winners.

TPC Scottsdale is a fairly easy course overall, with the field averaging 70.6 strokes/round for the week. The field averaged 301 yards off the tee (well above PGA average of 287 yards), hit 59% of fairways (slightly short of PGA average of 59%), hit 68% of greens (PGA average of 64%), and successfully scrambled 57% of the time (PGA average 58%). It’s clear that a combination of easy distance and little penalty for missing the fairway made hitting the green more likely.

Stadler as a player is definitely a much better ball-striker/driver than he is at putting or scrambling. He’s finished near the bottom in strokes gained putting in the last several years and he’s finished outside the top 100 in scrambling three of the last five seasons. In comparison, he’s been above-average in both driving distance and accuracy in the last few seasons, parlaying that and his approach shot skill into rankings of 33/26/8 in greens in regulation. We’re talking about a clear top top tier player from tee to green.

This week, Stadler simply played to his strengths, out-driving the field by 8 yards, hitting 9% more fairways, and using that great driving to hit 10% more greens than the field. His proximity to the pin was also 5 feet closer than field average. It helped that he successfully scrambled 12 of the 16 times he missed a green, which likely gained him something like 3 strokes on the field. However, his ability to put the ball in the fairway, further than most others, and then hit the green won him this tournament.

Digging deeper on his final round, I attempted to estimate his strokes gained for different types of shots. Prior work in this vein is here and here. I’m pretty confident in my numbers overall because 1) the course played roughly average in difficulty on Sunday and 2) my strokes gained on putts figure is within 0.3 strokes of the official PGA Tour number. My numbers show that three of Stadler’s best four shots on Sunday were approaches to the green – his approach to 3 feet on #14, his drive onto #17 green, and his approach to 4 feet on #9. In total he gained +2.1 strokes with his par 4/5 driving (14 shots), +1.3 strokes with his approach shots (4 shots), and +0.5 strokes with his par 3 tee-shots (14 shots), while he lost -0.4 strokes on 3 short shots around the green. I show his putting as having gained him no shots on the field in total.

I can explore this further, but it’s likely that Kevin Stadler played unusually well from tee to green for PGA tournament winners. His driving was superb in both distance and accuracy (a rare but potent combination) and he cashed in on those great positions by knocking his approach shots on the green and close.

What’s Changed – Zach Johnson

This week the Tour travels to Illinois for the John Deere Classic, a birdie-fest notable for the poor field it attracts in advance of next week’s Open Championship in Scotland. After winning last season, Zach Johnson has been installed as the second favorite by bookmakers and fantasy columnists, behind 2009-2011 champion Steve Stricker and ahead of Louis Oosthuizen and Keegan Bradley. This on its own is not particularly notable; past champions who also happen to be good players are considered favorites at most events, especially when the John Deere field contains only four of my top 25 players by both Z-Score and OWGR. What is particularly strange here is that Zach Johnson has been thoroughly mediocre so far this season. After a four year streak from 2009-2012 that marked him as a consistent top 25 player in the world by Z-Score (between -0.62 and -0.35 all four seasons), he’s fallen off precipitously to -0.13 over 51 rounds. Now, golfers play more poorly than normal over half seasons due to plenty of factors ranging from random variation to injury to genuine deterioration of skill. I’m not as concerned about whether Zach Johnson will continue to play well below his career average as I am interested in just why he’s playing so poorly this year and which parts of his game are responsible for the regression.

First, I will examine what made Johnson such a prolific player in past seasons, specifically focusing on 2012. This analysis will be using the Strokes Gained method, breaking down shots into Putting, Driving, Approach shots, and Scrambling shots. For this, I’ve created Strokes Gained – Driving, Strokes Gained – Approach Shots, and Adjusted Scrambling using publically available PGA Tour stats, and will use the PGA Tour’s own Strokes Gained – Putting stat. I have already explained how my Adjusted Scrambling stat is calculated; the other two will be introduced in coming weeks. For now, it’s important to know 1. the stats are measured in strokes above and below the field and 2. I try to isolate how well a golfer is performing in one area by adjusting for distance of shot, starting position, and what happens in subsequent shots.

Zach Johnson’s 2012 was a great season. He ranked 20th in the world according to my Z-Score Method, won two tournaments, earned four other top tens, and missed only a single cut. His success was driven by great putting and approach shots – he ranked 5th and 7th in those metrics, saving a total of 1.4 strokes relative to the field. His tee shots were a weakness, but cost him less than 0.1 strokes. He made up an equal number of strokes by scrambling well above-average, which combined with his great putting kept him out of bogey trouble when he missed the green. In short, he was as efficient as all but the most elite (Tiger, Rory, Adam Scott) golfers, performing well in three areas, while minimizing his losses in the weakest part of his game.

This season everything has gone off the rails. Starting with his approach shots, Johnson has fallen from 5th to barely above-average, and that’s the only part of his game that has even been above-average. He’s never rated highly in Greens in Regulation because, as a very short driver, he faces longer approach shots. Because of that it’s hard to get a sense of a decline in this area just by looking at the normally cited stats (he’s actually improved his GIR rank from 2012). In 2012, his approach shots yielded 2.72 expected birdies (sum of the probability that a birdie putt will be holed based on its distance). This figure ranked 45th on Tour, despite Zach Johnson hitting his approach shots from much further distances than most of the elite players. This year, he’s ranked only 112th.

More damaging has been his putting. Johnson was 7th on Tour in Strokes Gained – Putting in 2012, gaining 0.6 strokes on the field per round just from putting. For whatever reason, Johnson has really struggled on the greens this year and has essentially been average, losing 0.04 strokes versus the field this year. That itself is stunning. He had scored seasons of 0.38, 0.58, 0.57, and 0.60 strokes gained/round since 2009, and suddenly looks no different than the average Tour golfer at putting. I can speculate about all sorts of reasons for this decline – less practice, less preparation, age related yips, etc. – but obviously this is a huge problem. Johnson cannot return to his old form without regaining his putting stroke. Plenty of guys (Vijay, Adam Scott, Lee Westwood) are or have been great players despite not being good putters, but they’re fantastic tee-to-green players. Johnson needs to compensate for his inability to drive the ball far.

Johnson’s has struggled scrambling this year, but not to the point where it’s costing him more than a few hundredths of a stroke/round, and his driving hasn’t noticeably changed. But it’s apparent that all the decline we’re seeing from Zach this year is due to his inability to generate good looks for birdie and to putt at an elite level. I’d certainly bet on him regaining his form – he’s still only 37 and has extensive history of high level play – but I think it’s crazy to consider him a better player at this point than Keegan Bradley or Louis Oosthuizen.

Greenbrier Classic – Final Round

If we ever needed a lesson that golf is inherently random and statistics can only do so much to predict what will happen, Sunday’s final round at the Greenbrier certainly provided it. Johnson Wagner entered the final round leading Jimmy Walker by two strokes, with Jonas Blixt sitting three back. By the time Wagner was teeing off on #10 to start the back nine, Walker had not managed to close the gap at all, while Blixt had birdied #9 and #10 to get within a single stroke. From there, Blixt used several fantastic approach shots to set-up birdies, while Wagner made three crucial bogeys to fall out of the lead – handing Blixt his second PGA victory in less than a year. My analysis of the back nine will attempt to quantify strokes gained and lost on the field by each shot Wagner and Blixt made on the back nine, similar to my look at the Travelers.

What was remarkable random about the back-nine was what shots Blixt hit to set-up birdies. Blixt is fairly categorized a player very reliant on his putting for success (he was 2nd in 2012 and 47th this season). He does not hit his approach shots well, sitting nearly at the bottom in GIR, even when we account for his below average performance on tee shots. However on Sunday, Blixt’s two best shots were his approaches on #12 and #16 that set-up birdies – both worth around 3/4ths of a stroke. On the flipside, his normally sterling putting failed him on #11, #13, and #17 setting up two bogeys and depriving him of what would’ve been a decisive birdie.

On the par 5 #12, Blixt sat 108 yards from the hole after his lay-up. From there the average player hits to around 20 feet. Instead, Blixt hit a beauty to five feet, setting up a birdie that tied him with Wagner at -13. Later at the par 4 #16, Blixt was 173 yards in the fairway, a location from which the average pro hits to around 30 feet. Blixt hit an iron to nine feet, producing a make-able birdie putt that he drained to draw ahead of Wagner at -13. His approach here was his 2nd best of the day, behind the approach on #12, and his subsequent putt was his 3rd best shot.

However, along with those great approaches came three awfully poor putts which resulted in a par and two bogeys. On the long par 4 #11, Blixt missed the green, but chipped to 6 feet. PGA players make 2/3rds of those putts; Blixt not only missed but ran it three feet past, leaving a miss-able putt for bogey that he made. He hit another equally poor putt on the long par 4 #13. After laying-up, Blixt hit to 7 feet, but blew his par putt four feet past the hole. He would make the four footer for bogey. Again on the par 5 #17, Blixt was standing over a 7 footer that would’ve put him three clear of Wagner. Seven footers are 55% putts normally, so Blixt’s miss cost him over half of stroke, but at least he didn’t blow it several feet past the hole.

In total, Blixt’s back nine shots were worth: -0.44 strokes (tee shots), +1.85 strokes (approach shots), +0.48 strokes (short game), and -0.35 strokes (putts).

blixtgreenbrier

Johnson Wagner’s back nine was, succinctly, a disaster. He began it with a two stroke lead over Blixt that was quickly shortened to one stroke after Blixt’s birdie ahead of him on #10. At this point, no one else was any better than -11, while Wagner sat at -14. From there, Wagner bogeyed three of the next five holes and watched Blixt draw two strokes ahead of him for the win. For a guy who has been a steadily good putter (29th, 39th, and 41st in Strokes Gained in 2011-13), the flat stick failed him on Sunday. Two of his three worst shots were missed par putts inside 10 feet (on #11 and #13).

It was #15 that really sunk him though. He started #15 even with Blixt at -12. As we saw earlier, Blixt would go onto birdie #16, but Wagner would not have been in terrible position if he had parred #15 and moved on, as 16-18 aren’t difficult holes. His tee shot on the par 3 #15 was poor, ending up in the rough 14 yards from the pin. From there, PGA players bogey about half the time. Wagner blew his next shot 33 feet past the pin, leaving him a nearly guaranteed bogey. Within 15 minutes between Wagner’s bogey on #15 and Blixt’s birdie on #16, the  tournament was all but over.

For the back-nine, Wagner finished -0.23 strokes (tee shots), -0.17 strokes (approach shots), -0.71 strokes (short game), and -1.29 strokes (putts), a thoroughly miserable performance for a guy who is a PGA Tour player because of his ability to putt.

wagnergreenbrier

greenbrier component stats

 

What’s Changed? – Billy Horschel

One of the most significant stories on the PGA Tour this year has been the emergence of Billy Horschel as one of the best golfers week in and week out.. After racking up only three top-tens in his first two largely mediocre seasons on Tour, Horschel’s earned a top-ten in seven of seventeen starts this year, missing only a single cut along the way, and earning his first Tour victory in New Orleans. His arrival to the general golf public came at the US Open where he was in the final group Saturday and finished T4.

The incredible thing about Horschel’s emergence has been how poor he played in his first two years on Tour. He entered the Tour in 2010 through Qualifying School after a brilliant collegiate career at Florida, but made only four starts due to an injury. He re-earned his card in Qualifying School again, but had a poor year (+0.14 by my Z-Score Method & only 140th on the Money List). His conditional status in 2012 only allowed him to finish 147th on the Money List (-0.12 by Z-Score for PGA and Web.com rounds), but he managed to again qualify for the Tour in Q-School. So through two full seasons, he had shown himself to be roughly PGA average. In 2013, though, he’s played to -0.50 – the 18th best performance in the world.

While it’s not completely unheard of for a player to improve as much as Horschel did, it is very rare. Horschel’s improvement from 2012 to 2013 was -0.39 standard deviations. That is the 19th largest improvement from one year to the next in the last five seasons, from a sample of over 800 pairs of seasons (I restricted my examination to golfers with 50+ rounds in each season). Many of the improvements ahead of him are from golfers with established high levels of performance regaining form, such as Jim Furyk in 2012, Adam Scott in 2010, Sergio Garcia in 2011, and Angel Cabrera  this season. Whether due to nagging injury, personal trouble, lack of focus/preparation, etc. those guys fell from performing at a high level, but were able to regain their form the next season. Other golfers went from being extremely bad (below Web.com/European Tour average), to just mediocre. Much rarer  are the genuine breakthroughs where a golfer goes from being quite average to very good. Among those ahead of Horschel, only Webb Simpson in 2011 improved from average or better to playing elite level golf.

So how is Billy getting it done? What has he improved on since last season that has allowed him to earn the top 10s and maiden victory? To examine this I’m going to use what I’ll refer to as Component Stats. These are stats measuring how well a player scrambles, drives the ball, hits approach shots, and putts. To measure performance, I’ve created three of my own stats plus I’ll be using the publicly available Strokes Gained – Putting. For the other three, I’ve already introduced Adjusted Scrambling and I’ll be introducing my Approach and Driving stats in the next few weeks. For now, just remember that the stats are measured in strokes above and below the field and try to isolate how well a golfer is performing in one area by adjusting for distance of shot, starting position, and what happens in subsequent shots.

By this method, in 2012, Horschel was only substantially better than PGA Tour average at driving – where he gained nearly half a stroke on the field. He was average at scrambling, slightly below average at putting, and slightly above average at hitting approach shots. In short, he was much like dozens of other Tour golfers who survive because they’re very good at one skill and good enough at everything else. What separates the elite from those golfers is the elite only have one weak spot in their game. Of the best 25 golfers by Z-Score in 2012, only Robert Garrigus ranked below average in more than one of the four statistical components. Only three of the top 50 (Ben Curtis and Lee Westwood also) ranked below average in more than one category. As long as Horschel could only rely on his driving, he was not going to be able to distinguish himself.

I have no particular insight into what Horschel changed in his preparation in 2013; people have credited maturity gained from working with a sports pyschologist. What I do know is that Horschel has delivered far better performances putting and hitting approach shots this season. His Strokes Gained Putting has improved from -0.09 to +0.50 strokes this season – one of the largest improvements year-to-year – and improved by almost a half a stroke on approach shots; a total improvement of a full stroke. Horschel’s driving has remained well above average, and though his scrambling has regressed by 0.20 strokes (he’s only successfully scrambling 59% of the time despite putting lights out overall and hitting from closer lies), that hasn’t hurt him much.

horschel12&13

 

 

 

 

 

 

 

 

All in all, Horschel’s improvement has been worth 2/3rds of a stroke. A to-be-posted regression analysis shows that golfers a stroke better than PGA Tour average earn ~$65,000/tournament more than average golfers or about $1.5 million over a typical season, just to provide a financial benchmark to evaluate his improvement.

The question now is whether Horschel can maintain his performance going forward. My research has shown it’s correct to regress samples of around half a season by adding 25 rounds worth of average performance. That would expect Horschel to perform at around -0.36, equal to something like the 35th best player in the world. My weighted and regressed two year Z-Score method predicts something similar. However, if Horschel has made genuine changes to his preparation and mental approach to the game, we may not be seeing a golfer playing above his head, but rather one pushing his ceiling higher.

An Accurate Measurement of Scrambling Skill

(This is the first of three planned posts explaining the flaws in commonly used stats for evaluating golfers’s skills at driving, hitting approach shots, and scrambling and laying out a replacement based on publicly available PGA Tour stats.)

The Scrambling stat was developed to measure how often a golfer avoids bogey after missing the green with their approach shot. That requires a golfer to (usually) chip or pitch onto the green and then hole a par putt. Scrambling is simply calculated by dividing successful scrambles (par or less) by total GIR missed. The average for PGA Tour players in 2012 was ~59%, indicating that, when missing the green, they made par a bit more than half the time.

Scrambling is often used to evaluate whether a player has a good “short game”. Luke Donald has ranked 5th, 8th, and 4th in recent years and is generally proclaimed as one of the best short game players on Tour, along with Steve Stricker, Ian Poulter, and Brian Gay (who all have multiple top 10 finishes in the last few years). However, what scrambling really measures is a combination of three skills. First, it measures what it purports to – the ability to hit chips, pitches, sand shots, etc. around the green close to the pin. But it also measures the ability to putt, because scrambling requires a putting stroke to finish up, and hit approach shots, because players hit their chips, pitches, sand shots, etc. from locations that vary in difficulty. A very good putter will have an inflated scrambling ratio because they make a lot of putts after leaving their ball short of the hole that an average putter would miss. A good approach shot player will have an inflated scrambling ratio because when they miss the green, they leave themselves closer to the pin and in better locations (fairway or fringe instead of bunker or rough).

So with those shortcomings, how do you see through the noise and capture only the ability to hit good chips, pitches, sand shots, etc.? I first downloaded the PGA Tour data for scramblings from >30 yards, 20-30 yards, 10-20 yards, and <10 yards. This data represents all scrambling shots taken in tournaments where ShotLink is used (US based tournaments except Majors). I then found each golfer’s GIR in ShotLink measured rounds. Then I calculated how often PGA Tour golfers successfully scramble from each of the aforementioned distance bins (>30 yards – 27%, 20-30 yards – 52%, 10-20 yards – 64%, <10 yards – 85%). I then adjusted each players data to find how often they shot from each of the four distance bins, then multiplied that number by how often the average golfer successfully scrambled from that distance. The result for each golfer is how often the average PGA golfer would be expected to scramble successfully based on where that golfer hit their scrambling shot from. That solves the problem of golfers hitting from varying locations.

To adjust for putting skill, I downloaded each golfer’s Strokes Gained Putting for 2012. This stat measures how well a player putts compared to PGA average based on the length of the putt (ie, players who make more 20 footers than average will be above-average). I threw Strokes Gained Putting into a linear regression with Strokes Gained Putting and the earlier calculated expected scrambling by distance stat as the independent variables and a golfer’s overall Scrambling ratio as the dependent variable. I had 191 golfers in the regression. My R=0.70, which indicates that Putting and location of the shot explains 70% of the Scrambling stat, which is extremely large for a stat that is used to rank golfers ability to hit around the green. Both SGP and expected scrambling by distance were significant at the 0.001 level. The regression produced an equation (y = -0.038+(1.061*Putting)+(.0659*Location). I calculated the Expected Scrambling stat from that equation for each golfer. This measures how often a golfer should get up-and-down given a certain skill at putting and a certain location before the scrambling shot. When adjusting for these factors, Bo Van Pelt, Luke Donald, Brandt Snedeker, and Zach Johnson faced the easiest scrambling situations, being expected to make par or better on 65% of their missed greens.

From their, determining actual skill around the greens was simple. I subtracted a golfer’s Expected Scrambling from their actual Scrambling performance. The result indicated how much more often a player successfully scrambled, corrected for the location of their scrambling shots and their skill putting.

Top 10 and Bottom 10 in Adjusted Scrambling:ImageSeveral of the golfers in the old Scrambling rankings look good based on this adjusted ranking – Dufner, Poulter, and Rose were in the top 10 before and remain there again. But most of the rest were not highly rated by old Scrambling, highlighted by Nick O’Hern ranking  93rd (roughly average) in Scrambling despite being a poor putter and hitting his shots from the 2nd worst locations of anyone on Tour.

The trailers are more reflective of the old Scrambling rankings, though Bo Van Pelt was ranked 104th in scrambling by the old system, but because of he putted very well last year and hit from the best locations, he comes out 2nd worst in this ranking.

It is worth noting that this analysis ignores the difficulty of courses played. It’s probable that certain courses are more difficult to scramble successfully on, while others are easier. In his seminal Assessing Golfer Performance on the PGA Tour Broadie found that there were differences in course difficulty (~4 strokes between the most & least difficult), but that they were heavily concentrated in the long game (drives and approaches over 100 yards). The difference between the ten most difficult and ten least difficult courses overall was only 0.3 strokes when considering the short game (basically any shots inside 100 yards). His definition of short game means scrambling shots considered above make up roughly 2/3rds of the shots considered. I would expect that differences in scrambling difficulty by courses shouldn’t affect these adjusted Scrambling numbers by more than 2%, though I will revisit the topic of course difficulty in a future post.