On Dominance In Golf
Acres and acres of sand. Just as the landscape of the deathly-difficult and oft-treacherous Bethpage Black Golf Course is strikingly dominated by the ubiquity of bunkers, the 2019 PGA Championship field at the Long Island course was dominated, fittingly, by a long-driving and supremely confident Brooks Koepka.
Coming in as defending PGA champion from Bellerive last year, Brooks started ablaze, posting a course-record first round with a bogey-free 63. For good measure he followed that up with a 65-shot second round to set a new record for the lowest 36-hole score in a Major Championship and position himself with a 7-shot lead at 12-under. He then proceeded to shoot 70 in round 3 to maintain his 7-shot lead at 12-under par going into day 4.
Despite his best efforts at capitulation with 5 bogeys in the last 8 holes of round 4, he was able to hang-on and close out at 8-under for the tournament, beating Dustin Johnson into second — the only man in the field to shoot four sub-70 rounds — to retain his PGA crown by two shots.
Setting course records and new Major Championship lowest scores are, by their very nature, rare, impressive and hugely special feats. But what’s particularly impressive about Koepka’s feat at Bethpage is that he did so whilst the rest of the field limped around the course, way back in the distance. Brooks Koepka shot 8-under par whilst only five other players from the 82-man field were able to post an under-par score — DJ at 6-under, Cantlay, Spieth and Wallace at 2-under, and Luke List at 1-under. In total that’s 7% of the field shooting under par.
To put that in context, across the last 14 Majors, dating back to the beginning of 2016, 33% of all final scores have been under par. That ranges considerably on a tournament-by-tournament basis, with not a single player from the 67-man field at last year’s US Open able to break par at Shinnecock, whilst at the other extreme 73% of last year’s PGA Championship field were able to post scores under par. 7% of the field shooting under par is low, and Shinnecock aside, the only other time in the last 14 Major tournaments that fewer than 7% of the field have shot under par was at the US Open in 2016 where only 4 players (6% of the field) went under par in a Dustin Johnson win at 4-under.
At a tournament where so few players are able to break par, a score a few shots under par is broadly where you’d expect a winning score to fall given the average difference between each position at the Majors is just 0.4 points. As such DJ’s winning score of -4 at the US Open in 2016 was broadly inline with what one might expect given the relative performance of the rest of the field. Given the similarities in the overall performance of the field at the 2016 US Open and 2019 PGA Championship, a winning score to match DJ’s -4 would have been about par for the course at Bethpage.
Brooks doubled it, shooting -8 and blowing away the rest of the field (except for Dustin Johnson).
Koepka finished an average of 7 shots ahead of the each of the rest of the players in the top 10, 8.7 shots ahead of the rest of the top 20, and an average of 14.7 shots ahead of every other player in the field. His average number of shots ahead of the top 10 is the third-highest from the last 14 majors, marginally beaten by Spieth at the 2017 Open (7.1) and blown out of the water by the monster outlier of Stenson at the 2016 Open (14.9). His average number of shots to the top 20 and to the whole field rank second and third respectively.
Comparing these metrics to performances at the other Majors begins to build a picture of the dominance in Brooks’ performance, but what I really want to capture — and what I believe best illustrates his dominance — is the fact that he was able to post a low score of -8 in a relatively high-scoring field. I want to be able to quantify that he was able to shoot low when everybody else was shooting high and give that context against other Major Championship performances.
I believe the best way to do this is take the range of the field i.e. the difference in score between first place and last place and then use the percentage of players under par to approximate an Expected Winning Score. Applied to the 2019 PGA Championship this would give: a -27 score differential between first and last, divided by 7% (the percentage of players under par) to give an Expected Winning Score of -2 (based on an average of 0.4 shots difference between each position on Major leaderboards this assumes a distribution of players across all scores within the 27 point range and uses par as an anchor value from which to calculate an expected winning score based on the percentage of the field under par).
If we then compare the actual winning score to the expected we can see that Brooks went 6 shots under, underlining his vast superiority over the rest of the field. Because this metric is based on the aggregated performance of the field as a whole, out-scoring the Expected Winning Score provides a good measure of a player’s ability to outperform the rest of the field.
Across the last 14 Majors, Koepka’s -6 performance against expected is second only to Henrik Stenson’s monster out-performance of -11.4 at the 2016 Open at which he shot 20-under, 3 shots ahead of Phil Mickelson in second and 14 shots clear of J.B. Holmes in third.
Brooks is also one of four players from the sample to underperform against their Expected Winning Score, that during his US Open victory of 2017 where he shot -16 but came up 2.1 shy of the Expected Winning Score of -18.1.
Across the last 14 Majors the difference to expected averages out at -2.4 (in no small part to Stenson’s -11.4), exceeding +/-2.5 on only 4 occasions.
In conclusion, Brooks Koepka is pretty dominant right now, taming Bethpage Black in dominant fashion to win his fourth Major in the last 24 months, becoming the first player ever to hold two Major titles back-to-back simultaneously (assisted by the re-shuffle of the dates for the PGA Championship).
