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July 1, 2013 5:00 am
How pitchers can throw more pitches inside the strike zone and walk more batters (and vice versa).
I remember once that there was an article (not written by me, but it might as well have been; I’ve certainly written a version of this article before) that looked at a batter’s increased walk rate and concluded that it was due to... not swinging at as many pitches outside the strike zone. Colin Wyers tweeted something in response that went something like, but not exactly like, this: “uh no doy.” I try to keep that tweet (or at least something like that tweet) in mind, because it’s easy to find explanations that are already embedded in that which you seek to explain. Baseball generally obeys its own physics. Player is struggling because his heat map looks awful. Fielder’s numbers are down because fielder isn’t making plays in front/in back/whatever of him. Pitcher is walking more batters because pitcher is throwing fewer pitches in the zone.
But what about when that last one isn’t true? There are 179 pitchers who threw at least 1,000 pitches last year, and have thrown at least 500 pitches this year. The correlation between year-to-year changes in zone rate and changes in unintentional-BB rate is fairly modest: about .4. That means there must be a lot to not walking batters other than throwing pitches in the strike zone.