Removing the Mask: How Catchers Earn Extra Strike Calls

From Mike Fast at Baseball Prospectus on September 21, 2011:

Catchers play a central role in the game of baseball through their involvement with every pitch that their pitchers throw. One of their key tasks is receiving borderline pitches without discouraging the umpire from calling strikes.

Dan Turkenkopf was one of the first analysts to investigate this phenomenon using detailed pitch location data. He found that catchers differed significantly in their performance at getting strike calls from umpires. Matthew Carruth and Bill Letson followed up with additional research and similar conclusions. The size of the effect that Dan and Bill found was so large as to be almost unbelievable.

Earlier this year, I observed that where the catcher set the target relative to the edge of the strike zone and whether the pitcher hit the target had a large impact on the likelihood of a strike call. Some pitchers, such as Tom Glavine and Livan Hernandez, were consistently able to expand the edges of the strike zone by several inches. The fact that catchers are paired with a limited number of pitchers in a season affects our ability to properly assign credit for extra strike calls to catchers. Adjusting for pitcher-catcher pairing reduces the apparent size of the catcher responsibility for the effect to more reasonable levels.

When I reported this observation, I applied a pitcher adjustment to Bill Letson’s catcher receiving numbers from 2008-2009. Now, having added catcher defensive information to my own pitch database, I am in position to report my own measurements of catcher performance at getting extra strikes for their pitchers.

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Originally published: September 22, 2011. Last Updated: September 22, 2011.