A Deeper Look At Plate Discipline

There has been a lot of talk around the baseball world lately about patience and plate discipline. It started with Tom Verducci's Sports Illustrated article, which led to reactions by BP's Russell Carleton and our own Ryan Potter. Verducci claimed hitters are taking too many pitches, especially in hitter's counts, leading to more K's and a decrease in runs scored. Carleton showed how foul balls have increased early in the count, a bigger reason for the strikeouts. Ryan showed that the decrease in runs is as much of a product of the normal cycles of scoring in history as anything else.

Very intrigued by this whole discussion, I developed a large database using B-R's pitches category since the first available data in 1988. I added league averages each year, creating indices for many of the stats. The indices do not directly help test Verducci's claim, but knowing how teams do in comparison each year is helpful. My main metric of performance is runs per game, not wins as Verducci used. There are no park factors applied, but I believe it is still the best stat to use.

Verducci's first gripe came with the perceived taboo by swinging 3-0. There is a .12 correlation between swinging 3-0 and R/G, but there is a .38 correlation between getting to 3-0 counts and runs. I think hitters should only be swinging 3-0 if they have a great ability to leave the defense out of the equation, a.k.a. hit the ball out of the park. Teams who hit more home runs generally score more runs, so encouraging all teams to swing more 3-0 would be counterproductive. B-R also has 3-1 and 2-0 counts in their database. 3-1 swing% has a -.08 correlation with runs, while getting to 3-1 is at .48. For 2-0, swings correlate at .02 and getting to that count is .48.

Verducci then created a table "attempting" to prove how not swinging at the first pitch has led to more K's and less runs. The table does a horrible job of showing his point, and his point is probably not even true. Teams have a -.23 correlation between first pitch swing index and runs per game over the 25 seasons. It's not a strong correlation, but teams who swing less at the first pitch tend to score more runs.

His next point is that pitches per PA does not correlate with wins. First, comparing an offensive stat with a stat involving all facets of the game is just silly. Second, P/PA has a .31 correlation with R/G, so seeing pitches has resulted in more runs over the years. A couple other correlations: swing% vs. R/G is at -.36, percentage of strikes (not K's) that are looking vs. R/G is at .17, and contact% vs. R/G is at .23.

This is not proof that patience is better for hitters, but it's safe to say that Verducci's claim that patience is hurting hitters is not true. Personally, I think good hitters should swing more in hitter's counts, especially 2-0 and 3-1. Hitters with average or less power have no reason to swing 3-0, unless the pitcher is hitting behind them. Pitchers will likely start pounding the zone more on the first pitch, which will lead to another adjustment by hitters swinging more. There are fewer runs being scored the past few years, but patience at the plate is not the cause.