Strokes Gained Off The Tee: Going Long with Dustin Johnson

He had the best driving season on Tour in 2018…but how did it rank with other strokes gained driving seasons since the inception of Strokes Gained Off The Tee?

Measured by Strokes Gained Off The Tee, Dustin Johnson was the PGA Tour’s best driver of the ball during 2018. When the Tour Championship concluded the season, Johnson’s 0.92 score ranked first among 193 players who completed enough rounds to qualify for consideration.

But how does Johnson’s performance off the tee compare with the best efforts of his predecessors?

True, since the concept of Strokes Gained was first calculated on Tour during the 2004 season, Bubba Watson has the best single season raw number, 1.485 in 2012. But far too many variables play into Strokes Gained Off The Tee to merely rely on a raw number count when considering performances across time. Equipment changes, the ever-changing roster of players – with their divergent skill sets – weather and the changing panoply of courses combine to invalidate such a simplistic approach.

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In any kind of comparison over time, what is needed is a relativistic statistic that factors in – neutralizes might be a better word – all the year-to-year changes that would otherwise complicate such a comparison to the point of hopelessness.

There is such a tool: standard deviation. Because standard deviation measures the relative excellence of any performance against a fixed set of competitors under the same course and weather conditions, it provides the required neutrality.

The key is this: Instead of asking what Johnson’s score was compared with Watson’s in 2012, we need to ask whether it was more or less exceptional – compared with his 2018 competitors – than was Watson’s when measured against his 2012 competitors.

Measuring exceptionality is not a complicated practice; in effect, what we’re doing is aligning every competitor in every individual season along a gigantic bell curve, and seeing who winds up farthest out on the edge. In any set of data – such as the Strokes Gained Off The Tee totals for 193 PGA Tour pros in 2018 – about two-thirds will wind up within one standard deviation of the field average. Most of the rest will fall within two standard deviations of the average, while a handful – maybe two or three percent – will stand outside the two standard deviation barrier. That’s not my rule, it’s math’s rule.

By the way, those placings can occur on either the good or bad side of the curve.

In 2018, two of the 193 pros exceeded the 3 standard deviation performance barrier – and both fell on the bad end of the bell. With a -1.443 Strokes Gained Off The Tee, Wesley Bryan was 3.803 standard deviations below the field average of +0.04, one standard deviation equaling 0.39 in 2018. Cameron Tringale’s -1.351 Strokes Gained Off The Tee translated to -3.567 standard deviations worse than the field average.

Seven other players fell outside two standard deviations, of whom Johnson was the only one on the positive side. His 0.92 score was 2.256 standard deviations better than the Tour average. Luke List, second in Strokes Gained Off The Tee at +0.816, measured 1.990 standard deviations better than the average.

(For the record the six players finishing between two and three standard deviations worse than average were Whee Kim (-2.021), Derek Fathauer (-2.044), Daniel Summerhays (-2.608), Ricky Barnes (-2.715), Michael Kim (-2.726) and D.A. Points (-2.844). Their strokes gained scores fell between Kim’s -0.748 and Points’ -1.069.

With that method as a measuring stick, it becomes easy to contextualize Johnson’s 2018 performance off the tee relative to all others since 2004. And let it first be noted that Johnson himself is a frequent presence on such a list, with five of the 25 best seasons for Strokes Gained Off The Tee as measured by the standard deviation of exceptionality.

Here’s how those five Dustin Johnson seasons compare with each other:

Season SG driving St. dev. Rank (since 2004)

2016 1.117 2.79 6
2011 0.912 2.49 T15
2015 0.960 2.49 T15
2017 1.002 2.40 20
2018 0.920 2.26 23

Note that Johnson’s 2011 season, while only his fifth best when measured by raw Strokes Gained Off The Tee, actually equaled his second most exceptional as measured by standard deviation. How can this be? During that 2011 season, the standard deviation of tour performance in Strokes Gained Off The Tee was just 0.35 strokes, the smallest in the past decade. In short, driving performance was homogenized that season, a factor that magnified Johnson’s superiority.

How about Watson’s 2012 season, the one in which he set the numerical standard of 1.485 strokes gained driving? When we do the math, it ratifies Bubba’s standing as the best, most efficient and most exceptional driver of the Strokes Gained era.

Here is the full list of 25 most exceptional seasons since 2004 as measured by the standard deviation of each player’s performance in Strokes Gained Off The Tee:

Season Name SG driving St. Dev.

2012 Bubba Watson 1.485 3.71
2014 Rory Mcilroy 1.367 3.60
2015 Bubba Watson 1.194 3.12
2016 Rory Mcilroy 1.230 3.08
2005 Sergio Garcia 1.003 2.86
2016 Dustin Johnson 1.117 2.79
2005 Kenny Perry 0.949 2.70
2005 Vijay Singh 0.870 2.66
2012 Rory McIlroy 1.072 2.65
2004 Vijay Singh 0.870 2.59
2006 Adam Scott 0.955 2.56
2005 Tiger Woods 0.896 2.55
2007 Boo Weekley 0.876 2.53
2013 Bubba Watson 0.967 2.52
2014 Bubba Watson 0.937 2.49
2011 Dustin Johnson 0.912 2.49
2015 Dustin Johnson 0.960 2.49
2011 Bubba Watson 0.898 2.45
2016 Bubba Watson 0.983 2.44
2017 Dustin Johnson 1.002 2.40
2007 J.B. Holmes 0.828 2.39
2008 J.B. Holmes 0.866 2.31
2018 Dustin Johnson 0.920 2.26
2017 Jon Rahm 0.935 2.23
2008 Vijay Singh 0.819 2.19

The final question is whether superiority in Strokes Gained Off The Tee makes any difference in terms of scoring well? We can get one indicator by scanning the list above. It contains the names of six players who led the Tour in scoring average: Singh in 2004, Woods in 2005, McIlroy in 2012 and again in 2014, and Johnson in 2016 and again in 2018.

But that kind of cursory examination doesn’t really establish much. What we need to do is measure the strength of the player-by-player relationship between Strokes Gained Off The Tee and scoring average.

Regression analysis, which provides that measurement, puts the average strength of any relationship involving two numbers on a scale between zero — no relationship whatsoever — and either 1.0 or -1.0, depending on whether the two numbers move in the same direction or different ones. In terms of driving (where higher is better) and scoring (where lower is better), the goal is to get close to -1.0 and as far from zero as possible.

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Here’s the answer: Since 2004, the relationship between Strokes Gained Off The Tee and scoring average is -0.497. In 2018, the relationship is -0.60. Bottom line, Strokes Gained Off The Tee is a significant, although not overwhelming, contributor to scoring.

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