By: Edward Egros

putt

Predicting Putts on the PGA Tour

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If you go to your favorite search engine looking for studies on predicting the likelihood a PGA Tour player sinks a given putt, you will find enough research to suggest there is no other dimension for discovery. Distance and slope largely affect the odds a golf ball finds the bottom of the cup. Golf tournaments have even begun broadcasting both this research and these resulting probabilities as part of its televised coverage.

What you don't see in a lot of research or in broadcasts is how these odds can be adjusted based upon the golfer himself. Suffice to say, some players are better putters than others.
While statistics like Strokes Gained: Putting can be volatile, the results from specific golfers can be used to calculate a more accurate probability that any given putt will be successful.

With the help of students at Southern Methodist University, we put together a model for predicting the probability of a successful putt. Using data from 2014 to the 2018 seasons, we first used the following variables:

  • Distance (in inches)
  • Distance^2 (the squared term for distance)
  • Resulting Score (e.g. birdie, par, bogey, etc.)
  • Hole sequence (i.e. the player's progress throughout his round)
  • Position on the Leaderboard
  • Slope (uphill, downhill or level)
  • Interaction terms between slope and distance, as well as slope and distance^2
  • Par value
  • Specific golfers (Binary variables that equal 1 if the putt will be taken by a specific golfer, otherwise 0)

Pertaining to that last set of variables, for this study we took 20 of the more popular golfers on the PGA Tour with varying putting prowess:

  • Adam Scott
  • Brooks Koepka
  • Bryson DeChambeau
  • Bubba Watson
  • Dustin Johnson
  • Henrik Stenson
  • Jason Day
  • Jon Rahm
  • Jordan Spieth
  • Justin Rose
  • Justin Thomas
  • Patrick Reed
  • Phil Mickelson
  • Rickie Fowler
  • Sergio Garcia
  • Tiger Woods
  • Tony Finau
  • Webb Simpson
  • Xander Schauffele
  • Zach Johnson

Because of the pressure of winning a golf tournament and because the sample after the second-round cut only features players who have played well enough to post low scores, we constructed two model: one to represent the first three rounds of a Tour event and one for the final round. These models are
logistic regressions, with the coefficients for each variable representing an odds ratio. Before analyzing specific golfers, here are the results for the other variables:

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Even though some of these coefficients are close to one and perhaps difficult to analyze, all are statistically significant and logically intuitive. For instance, as distance increases, the putt becomes tougher. A downhill putt is tougher than an uphill putt. Bogey putts tend to be easier to make than pars and birdies (perhaps because they tend to be the second putt in a sequence where a golfer has learned how to read the green better).

As for the golfers themselves:



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These bar charts represent who tends to be better putters, and there are many observations available. In no particular order, Henrik Stenson is one of the more exceptional golfers with the flat stick, though there is a slight drop-off as the tournament concludes. Rickie Fowler performs consistently well, especially when he is in contention. Bryson DeChambeau has putted well in his victories, but it was a skill he had to work on during his professional career. Tiger Woods has a natural uptick when he is competing for a win. Lastly, when Jason Day or Jordan Spieth have momentum heading into the final round, they exhibit solid putting abilities.

There are many things that could improve this study. Our data did not include weather information, which affects greens (dry greens are faster and tougher, wet greens are slower and easier). There also isn't a way to analyze newer golfers who have not played in many PGA Tour events. Perhaps there is a way to convert other data and translate it to PGA Tour levels, but that is not at our disposal right now. Still, the results here are promising and should help refine the probability of putts when dealing with specific golfers.

Special thanks to
ShotLink for providing the data. Also, we put together a GitHub page with academic presentations, R code and other valuable information. For that, click here.

Is Jordan Spieth Struggling?

IMG_3376Even before winning two majors—and nearly two more—in 2015, Jordan Spieth was one of the more popular golfers on the PGA Tour. Then, that popularity soared when the 22-year-old set many records beginning with the phrase: "Youngest golfer to…". But with enormous popularity and early success come high expectations. This year, Spieth has not won a major, only being in contention once out of three times. He also fell out of the top spot in the Official World Golf Rankings and has three fewer victories overall. Given what he did accomplish and how he's performing now, is Jordan Spieth Struggling?

Spieth defended his record and, during his performance at The Open at Royal Troon Golf Club, felt any questions about struggling was "unfair". Per
golflink.com:

"It's been tough given I think [2016 has] been a solid year," said Spieth. "I think if last year had not happened I'd be having a lot of positive questions and instead most of the questions I get are comparing to last year and therefore negative because it's not to the same standard…So that's almost tough to then convince myself you're having a good year when nobody else really…even if you guys think it is, the questions I get make me feel like it's not. So I think that's a bit unfair to me…"

Let's take an analytical look at if Jordan Spieth is struggling by his standards and, if so, by how much. The simplest way is to look at
Strokes Gained rankings and compare last year to this year. What makes Strokes Gained so useful is pointing specifically to the parts of the game a golfer may or may not be excelling at. The following statistics compare how well Spieth has done compared with the rest of the field:

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The numbers above the bars are his rankings on Tour. What also matters here are the following equations:

Off-the-Tee + Approach-the-Green + Around-the-Green = Tee-to-Green

Off-the-Tee + Approach-the-Green + Around-the-Green + Putting = Total

First, Spieth is actually performing better off the tee, but the rest of the field has caught up. Around the green and putting have remained steady or actually improved. The glaring statistic is his approach to the green. This measures all approach shots on par-4 and par-5 holes that are NOT within 30 yards from the edge of the green and includes tee shots on par-3 holes. Spieth has gone from .618 to -.016 (moving from 11th place to 118th). This statistic is further highlighted by looking at the breakdown of his rankings compared with the rest of the field:

  • 163rd in Greens in Regulation Percentage (62.3%)
  • T107th in Approaches from 75-100 yards (17' 10")
  • T109th in Approaches from 100-125 yards (20' 5")
  • T118th in Approaches from 125-150 yards (23' 9")

This information explains the discrepancy in SG: Tee-to-Green and SG: Total. It also explains the bigger discrepancy in tee-to-green versus total, because his skill at putting is included in the total, not tee-to-green. It is also worth noting, Spieth is playing in fewer tournaments this year than last. He played in 25 last season and is only through 16 this season, prior to the PGA Championship.

Let's now look solely at majors and highlight the discrepancy in Spieth's approach game:

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Spieth does not have the same driving accuracy, greens in regulation numbers or sand save percentage that he did in that record-breaking year.

Here is something else to consider. Perhaps one of Spieth's strengths is adapting to links courses. PGA Tour players do not play a lot on these types of courses, and while other golfers can drive the ball farther, this skill is not an advantage on a links course. But Spieth's skills as a putter and around the green do come in handy. In 2015, the U.S. Open was on a links course. Spieth won. This year, the only two domestic tournaments that even come close to those types of conditions are the AT&T Pebble Beach Pro-Am and the Hyundai Tournament of Champions. Spieth won the latter.

What Spieth said about his game and his year requires clarification. Strokes gained statistics have helped us highlight two important things about Jordan Spieth. First, his approach game has let him down much more so than last year. Second, he is not struggling with any other part of his game and in some ways he has improved. While his fans hope Spieth would have won more tournaments this year, he still has virtually as good a chance as any to capture the final major of the season.