First-Batter Walks: The Sequel
Last week, I investigated something that I’ve long wondered about: are relievers particularly prone to wildness on their first batter of the game? I didn’t find much of an effect, and I also got tons of valuable feedback about further avenues for investigation. Do base/out states matter? Does handedness matter? Do intentional walks skew the data?
Aside from the last one (a definite yes), I haven’t explored all of these avenues yet. I did, however, answer another question I was curious about, one that ties into the general theme of reliever walk rates. I’ll tell you upfront that I found a confusing result, and that I’d love to hear anything I’ve missed or avenues for further investigation.
Here’s the question I’m answering: when a reliever walks the first batter he faces, what does that tell us about the rest of his appearance? All of us have seen this in practice, and we probably all know the existential dread it engenders. Great, he doesn’t have his command today. How many walks are coming up? Is the lead safe? Will the team even stay in the game long enough for a new pitcher comes in?
To explore this possibility, I examined every game thrown by a reliever since the beginning of the 2015 season. I split each reliever’s appearances into two subsets: every appearance where they unintentionally walked the first batter they faced on one hand, and every other appearance (except intentional walks, I threw those out) on the other. This gave me a sample of 1,085 relievers across more than 80,000 appearances. Read the rest of this entry »