Lang: Analyzing the strike zone as a three-dimensional volume

From Eric Lang at The Hardball Times on September 15, 2015, with mention of SABR member Jon Roegele:

The strike zone has come under heavy fire lately from the analytics community, as the zone has expanded greatly in recent years — particularly here at The Hardball Times by the excellent Jon Roegele — and helped contribute to the decrease in run scoring. It’s an issue, But there is another interesting topic involving the strike zone conversation: the strike in three dimensions.

The strike zone is defined by the MLB rule book as the area over home plate that extends from midway between the belt and shoulders of the batter down to the bottom of the knees.  The latter part of the definition is not new; however, it did come as a surprise to me to learn that that strike zone covers the entire plate and forms a pentagonal volume.

Most baseball fans, and arguably players, would assume that pitches are called as balls or strikes based on their position at the front of home plate. However, the rule book defines a strike as a pitch where “any part of the ball passes through any part of the zone.” Therefore, a ball that simply passes through the strike zone for a total of one inch should technically be called a strike. This is where you may think of back door strikes: the slider that catches the outside corner of the plate.

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Originally published: September 15, 2015. Last Updated: September 15, 2015.