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Tag Archives: 2012

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.

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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.