Home Plate Umpire Positioning

From Mike Fast at Baseball Prospectus on September 7, 2011:

We have known for several years that right-handed and left-handed batters do not see the same strike zone in the major leagues. The strike zone for left-handed batters shifts about two inches toward the outside. This observation goes back at least to Dr. John Walsh’s analysis of PITCHf/x strike zone data in 2007.

In my analysis of the strike zone earlier this year, I suggested the following:

For example, as mentioned earlier, the zone for left-handed batters is shifted toward the outside. Do umpires have some bias against left-handed hitters? If so, why? Perhaps a more likely explanation is that they simply call more strikes outside to lefty hitters because that’s where the catchers are setting their targets, and the umpires are using the target as a cue. While right-handed batters see 58 percent of pitches outside of the midpoint of the plate, left-handed batters see 66 percent of pitches on the outside half. The average pitch to a left-hander is 2.4 inches farther outside than the average pitch to a right-hander, which dovetails nicely with John Walsh’s finding that the average strike zone for a left-handed batter was shifted 2.3 inches farther outside than the average zone for right-handed batter.

Today, I want to investigate an alternative explanation, not because the above explanation is faulty or insufficient, but rather as part of the process of understanding the strike zone and how home plate umpiring works.

While researching hit batters, I observed that the umpire positioned himself differently on inside pitches to Chase Utley and Raul Ibanez. It turns out that changes in umpire positioning are not a rare event.

I decided to track the position of a home plate umpire’s head over multiple pitches.

Read the full article here: http://www.baseballprospectus.com/article.php?articleid=14951

This page was last updated September 7, 2011 at 11:44 am MST.