Choiniere: The new strike zone’s potential effect on batters

From John Choiniere at Beyond the Box Score on March 6, 2016:

Back in January, it was reported that Major League Baseball was considering changing the rulebook definition of the bottom of the strike zone, raising it from the hollow below the knee to the top of the knee. According to Commisioner Manfred, this would be done in response to the ever-dropping nature of the strike zone, which has steadily proceeded downward through at least the PITCHF/x era (as shown by BtBS alum Jon Roegele). Anthony Castrovince recently published an article at that illustrated just how significant the change has been, and over at FanGraphs August Fagerstom recently looked at which pitchers would be worst-affected by the change. Although recent news indicates that there probably won’t be a change for this season, I’d still like to take a look at what such a change might mean from the batter’s perspective.

First, let’s remind ourselves what we’re talking about. Here are two strike zone plots, similar to what Jon reports for his size-of-strike-zone data. The principal difference is that he uses a strict threshold of 50% of taken pitches being called strikes, while I’m using color to illustrate likelihood of a taken pitch being called a strike. Since I used 1″ squares, by summing the probabilities I can get a strike zone size in square inches. By my method, I find that the strike zone in 2009 was 463 square inches, while in 2015 it was 498 square inches.

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Originally published: March 7, 2016. Last Updated: March 7, 2016.