## Strokes Gained When In Contention

This posts builds on an earlier post of ours that attempted to quantify pressure in golf. We construct a measure that is similar in spirit to the strokes-gained measures used by the PGA Tour to analyze putting, approaches, and driving. The purpose of this measure is to analyze which players perform the best when they get in contention to win a golf tournament relative to their normal standard of play, and also relative to how their peers perform when they get in contention.

First, I’ll outline how the measure is constructed:

1. Calculate the difference between a player’s score and the field average for that day. Call this the relative score.
2. Using only round 1 and 2 scores, calculate the average relative score for each player. This is meant to capture how a player plays relative to the field in low pressure situations.
3. Using only round 4 data, calculate the average relative score for each player in different “pressure zones”. For example, our “Playing Near/With the Lead” (PWL) zone is being in a position of 5th or better heading into the final round, and our “Chasing the Leaders” (CL) zone is being in 6th-12th place heading into the final round.
4. Let’s just focus on the PWL measure for now. For each player, take the difference between their average PWL relative score and their average relative score under no pressure.
5. To clarify, at this point we have a value for each player which indicates how much their average relative score differs between no pressure situations and the PWL zone. The final step is to calculate a weighted average of all these values (where the weights are equal to the number of times a player gets in the PWL zone). Then the “strokes gained in the PWL zone” will be a player’s value minus the average of all the players’ values.

If this was a bit confusing, an example will make it clear. Let’s calculate Tiger Woods’ strokes gained in the PWL zone as an example. This is done using PGA Tour data from 1983-2016.

• In rounds 1 and 2, Tiger’s average relative score is -2.4186.
• When Tiger is in the PWL zone (top 5 heading into the final round) his average relative score is -2.7168.
• So this says that Tiger plays 0.2982 shots better than his usual standard of play when he is in the PWL zone.
• Additionally, we calculate (by averaging all of the measures constructed like Tiger’s above) that the average player plays 0.118 shots worse when they are in the PWL zone. Therefore, we say that Tiger is gaining 0.2982 – (-0.118) = 0.416 strokes on the average player when he is in the PWL zone.

We are not trying to make the claim that this statistic is solely quantifying pressure. We think of it as reflecting a player’s ability to close tournaments, a player’s ability to continue a hot streak of good play, and also a player’s ability to perform under pressure. As much as possible, we want this to just be a descriptive statistic; it tells us whether a player tends to play better or worse than usual when they are in contention.

The main issue with this statistic is sample size. There are many players who have only made it into the pressure zones once or twice. In these instances, the statistic is uninformative with regards to that player’s true ability when in contention. Fortunately, using data from 1983-2016 on the PGA Tour, there are many players with a substantial number of trips to the PWL zone. The following table shows the strokes gained in the PWL zone (top 5 entering final round) for all players for which we have at least 40 observations.

To conclude, this statistic indicates how a player performs, relative to his usual standard of play, when he is in a pressure zone compared to how the average player performs in the pressure zone. This is analogous to strokes gained putting, for example, which indicates how a player performed on a specific length putt compared to how the average player performed on it.

## Dropping the Anchor

Prior to 2011, players using ‘long’ or ‘belly’ putters was fairly rare. Then this happened:

2011 PGA Championship –> Keegan Bradley (belly putter)
2012 U.S. Open –> Webb Simpson (belly putter)
2013 Masters –> Adam Scott (broomhandle)

These three major wins for the long putter sparked a reaction that led to many PGA Tour players switching and trying their luck with the long putter. It didn’t take long for the USGA and other organizations to enforce a rule that effectively banned the use of long putters. In 2013, they announced the ban would begin on January 1, 2016.

Well it’s been 3 years since the announcement, and 7 months since the actual ban was implemented. Seems like a good time to check in on the 3 players responsible for the ban.

In the graph below, I have plotted the average strokes gained in each half year for Webb Simpson, Keegan Bradley, Adam Scott, and Carl Pettersson (a long-time user of the long putter).