Do More Foul Balls Really Unnerve a Pitcher – Part 2

After some comments on the last blog post (“Do Foul Balls Really Unnerve a Pitcher”), I went a little deeper and looked at the number of foul balls for a fixed number of balls and a two strike count. The conclusion from just looking at the number of foul balls was that it appears that an increased number of foul balls unnerves both the pitcher and the batter. Looking at the number of foul balls based on the count reinforces this conclusion.

Batting Average

Based on seasons from 1988 – 2009, the batting average by number of foul balls and the place in the count is shown below.

As the number of foul balls increases for a fixed ball/two strike count, the batting average increases consistently. The batting average increases between 17 and 50 points over the zero foul ball batting average. It is possible that pitchers actually can become frustrated because they are unable to put the batter away early. The longer the batter stays alive, the more likely it is that they will actually get a hit.

Even though the batting average increases as the number of foul balls increases, the highest it reaches is about .250. The batting average is significantly lower for two strike counts with a fewer number of balls. This points to the unnerving of the batter with the overall lower batting average, and also with the decreasing batting average as the number of balls decreases.

There appear to be a number of factors influencing the result of the at bat, including whether the pitcher is behind or ahead in the count, as well as how long the plate appearance continues. The closer either the pitcher or batter is to losing the at bat, the more the pressure appears to increase.

On Base Percentage
The on-base percentage shows the same trend as the batting average except for the 3/2 count.

For two strike counts with two balls or less, the on base percentage increases as the number of foul balls increases. The amount that the OBP increases over the 0 foul ball count is about 17 to 50 points as well.

For the 3/2 count, however, the on base percentage increases by about 23 points for one foul ball and then stays fairly level as the number of foul balls increases. This is due to the fact that the walk rate for a 3/2 count is about 30% and remains consistent regardless of the number of foul balls. For the 3/2 count, batters end up on base in nearly one out of every two plate appearances.


Strikeout Rate

The strikeout rate by count and number of foul balls tells a similar story of the pressure increasing on both the pitcher and batter.

As the number of foul balls increases for a given count, the strikeout rate decreases. The longer a batter is allowed to hang around, the more difficult it is for the pitcher to put the batter away. This is also shown by the fact that as the number of balls increases for a two strike count, the strikeout rate decreases as well.

Data Source: http://www.retrosheet.org/