Bryson DeChambeau’s big problem: volatility

Bryson DeChambeau could certainly win the FedEx Cup this weekend at East Lake, but he probably won’t. The problem is volatility.

I’m not talking about the kind of emotional volatility DeChambeau occasionally displays on the course. His real problem is performance volatility: the natural ups and downs of his score that are occasioned by the uber-aggressive adjustments he’s made to his swing.

Those adjustments that emphasize power above all else inevitably induce volatility on the scorecard. From week to week, round to round and sometimes hole to hole, there is an unpredictability to DeChambeau’s game that is less present in the game’s of his top competitors.

It’s real, it’s measurable, and comparisons of the 10 FedEx Cup front-runners coming to East Lake illustrate it.

Since the U.S. Open, DeChambeau has had a 68.69 scoring average. Among the 10 Cup leaders, that stands only fifth for the time period, but the distinctions are so small that DeChambeau’s rank is essentially irrelevant.

The gap between the leader for that period, Jon Rahm (67.69), and the guy in 10th, Jordan Spieth (69.25), is only a fraction more than a stroke and a half. Looking purely at average, DeChambeau has the game to win.

His hangup is the standard deviation – the volatility if you will — of each player’s scoring. Standard deviation measures the usual range of a player’s performance. Player A may average 69, and Player B may average 70, but if Player A has a higher standard deviation — meaning his average score is less predictable — Player B may still be the more likely winner from week to week.

And that’s where DeChambeau runs into trouble. Since the U.S. Open, the standard deviation of DeChambeau’s scoring is 3.71 strokes. Among elite Tour players, that is an extremely high figure, and it essentially renders his day-to-day and week-to-week game unforecastable.

By comparison, the standard deviations in the scoring averages (since the U.S. Open) of the 10 players who enter the Tour Championship at the top of the FedEx Cup points list. The players are ordered by their standing on the list. Pay particular attention to the standard deviation column.

Player                                    Avg.       Std.  Dev.

Patrick Cantlay                  68.50         2.70

Tony Finau                          69.08         3.62

Bryson DeChambeau      68.69         3.71

Jon Rahm                            67.69         2.65

Cameron Smith                 68.35         3.49

Justin Thomas                   69/04        2.53

Harris English                     68.50        3.06

Abraham Ancer                  68.77        3.19

Jordan Spieth                      69.25        4.15

Sam Burns                           68.82        3.55

Since the U.S. Open, DeChambeau has the fifth-best scoring average among the 10, but at 3.71, he also has the second-worst standard deviation in his performance. Among the top 10, only Jordan Spieth, at 4.15 strokes, has been a more volatile player.

In statistical terms, all we can really say about DeChambeau’s game is that there is about a 70 percent likelihood of his finishing somewhere between 65 on the low end and 72 on the high end.

We can carry the math out to a second standard deviation. That gives us about a 95 percent certainty that DeChambeau’s round-to-round score will fall somewhere between 61 on the low end and 75 on the high end.

In other words, the numbers don’t really tell us much at all about what DeChambeau may do that we couldn’t have guessed merely by knowing what all pros do every week.

Contrast that with the consistency Cantlay has shown in seizing the No. 1 spot on the FedEx Cup list.

His 68.5 stroke average since the U.S. Open is only very marginally better than DeChambeau’s. But his 2.70 stroke standard deviation makes him a full stroke more predictable.

That gives us 70 percent confidence that Cantlay will shoot between 66 on the low end and 71 on the high end. Carried to two standard deviations, we have a 95 percent certainty that Cantlay will finish any round between 63 and 74.

Cantlay’s good numbers are not as good as DeChambeau’s, but the bad numbers are not as bad, and both are substantially more predictable.

In fact, if you run each competitor’s average performance since the U.S. Open across four rounds, then subtract the handicap advantage each will receive at the start of the Tour Championship, Cantlay’s biggest challenger at Atlanta isn’t likely to be either DeChambeau or the guy who starts No. 2, Tony Finau.

Here’s how those numbers work out.

Player                            4-round avg.      Hdcp.      Net

1 Patrick Cantlay               274                  -10          264

2 Jon Rahm                         271                  –   6         265

T3 Bryson DeChambeau 275                  –   9         268

T3 Tony Finau                    276                   –   8         268

T3 Cameron Smith           273                   –   5         268

6 Harris English                 274                  –    4         270

T7 Abraham Ancer           275                   –    4        271

T7 Sam Burns                    275                  –    4         271

9 Justin Thomas                276                  –    4         272

10 Jordan Spieth               277                  –    4         273

At 67.69 strokes, Rahm actually has the lowest scoring average (since the U.S. Open) of any players starting among the top 10. With a tiny 2.65 standard deviation in round-to-round performance, he’s also been the second most predictable, trailing only Justin Thomas (2.53).

In fact, Rahm would deserve to enter East Lake as the favorite, but for two factors, the most obvious being the four strokes, he’ll be spotting Cantlay. The other is that among the top contenders, Rahm has been decidedly the least active. Due to various reasons, he’s played only 16 Tour rounds since the Open; the group average is about two dozen rounds for that time period.