I.T.N. No. 20
PUBLISHED June 9, 2020
Inside The Numbers ...
is a brief numerical summary of the current happenings in the world golf, published every Monday — hopefully.
While stalling the PGA TOUR season before it could really get started, the global pandemic also provided some players a much-needed oppurtunity to reset — perhaps none more so than golf's golden child, Jordan Spieth. Prior to the hiatus, Spieth's 50-round true strokes-gained moving average was +0.4 strokes per round. While this may not sound that bad on the surface, it is eerily close to the form he showed as a junior back in 2011! The plot below shows Spieth's 50-round moving average since those amateur days... After a meteoric rise which culminated in 11 wins (3 majors), the game hasn't come so easy for Spieth in recent times. What began as putting woes in mid-2017 soon became significant off-the-tee and approach problems by 2018. In his "prime" Spieth was comfortably a top 5 approach player, but since then he has slipped below the level of an average tour player. In fact, if it weren't for Spieth's flat stick returning and surpassing previous levels in the past year, this could be looking a lot worse. On a positive note, Colonial Country Club is hosting this week, a course where Spieth has historically performed a full shot per round better than our model's expectation in 28 trips around the track.

Golf is better when the fiesty team of Spieth & Greller are near the lead; we hope he can recapture some of his former glory soon.
Over the break, we took the time to expand our score database to include a comprehensive set of amateur data. As a result, we now have amateur rankings and amateur true strokes-gained plots.

An obvious point of interest is to see how the best amateurs in the world compare to professionals. Since he is playing this week, let's look at the reigning U.S. Amateur champ, Andy Ogletree. In the latest edition of our amateur rankings, Ogletree was ranked 20th and has recently been performing at the level of an average European Tour player. So where does this put him in our pro rankings? He's currently ranked 585th, a daunting 565 spots below his amateur rank. As a reference point, Jon Rahm obtained the highest "professional" rank while still being an amateur; the week prior to turning pro (June 20th, 2016), Rahm was ranked 37th in our pro rankings.

What can we take from this? PGA TOUR players are really $&!@ing good, and there is no guarantee that top amateurs will "make it" (see Chris Williams, Bobby Wyatt).
In the past couple months we have made several additions to our model for predicting golf tournaments. Among them is the way we adjust for golfers' histories at a course; this adjustment is now broken into two components, 'experience' and 'course history'. As you might expect, golfers derive some benefit from having played a course in the past, regardless of how they have played. We find that, all else equal, playing 10 extra rounds at a course adds 0.05 strokes per round to a golfer's expected performance. This is the 'experience' component. (Separately, we actually examined experience at Augusta National in a past blog.) The second component takes into account how a golfer has performed historically at a course relative to our model's expectation for them at the time. Importantly, this expectation takes into account both a golfer's general skill level, and their course fit. This week, Kevin Na has the highest adjustment — +0.24 strokes per round — due to his history at Colonial, with 0.1 of these strokes being attributed to experience, and 0.14 due to past over-performance.
How was Emiliano Grillo's game trending before the PGA Tour season was postponed? Well, that depends which part of his game we are talking about. Grillo has always been good with his irons, but he has been an assasin of late, approaching the skill level typically possessed by the best approach player in the game (the blue line in the linked plot). We have Grillo ranked as 9th best in approach on tour, trailing only household names like Woods, McIlroy, and The Closer.

On the other hand, Grillo's recent putting trends have left a lot to be desired: Interestingly, we don't have Grillo rated as that bad of a putter: our current putting skill for Grillo — that is, how we expect him to perform in his next round — is only -0.21 strokes per round. While this is bad, it's not as bad you may have expected given the plot above. The reason for it is that to estimate a golfer's putting skill, it is best to take a very long-term view; one year of data is nowhere near enough to accurately assess putting ability. Therefore, Grillo's predicted putting skill is still well above that of a long-term bad putter such as Ben An. Putting it all together, we are applying a sizeable bump to Grillo's baseline skill this week due to his specific strokes-gained category performances.
One of the things we like to do most at Data Golf is underestimate Brooks Koepka. This week is no different, as we have 15 golfers in this week's Charles Schwab Challenge ranked ahead of the #3 OWGR-ranked player in the world. The hits kept coming this week for Koepka, as we released an all-time ranking of professionals since 2004, and of amateurs since 2010 — neither of which reflected particularly favourably on the Michelob Ultra spokesman. The list ranked players off their best stretches of golf, which placed Koepka at #37 on the professional list and #156 on the amateur list (1 spot above his brother, Chase). Coming back to this week, one thing Koepka does have going for him is that his recent play has largely been the product of a faulty putter; something which we shouldn't expect to continue going forward.