Mixing it Up: Changes in Pitch Usage
Predicting the future performance of baseball players is a wildly frustrating endeavor. When projecting a hitter’s stat line, it’s impossible to account for the player having a BABIP that’s nowhere close to their career average. When projecting a pitcher, it’s hard to know when their HR/FB rate is going to swing drastically away from their career average. The shifts in “luck” make projecting seem like a fool’s errand at times.
But it may be even more frustrating when something within the player’s control changes completely. When predicting the future, you largely have to rely on the assumption that what the player puts into the equation will remain relatively the same. But of course that’s not the case. Hitters will lose plate discipline out of nowhere. Pitchers will lose the ability to induce swings and misses. It just happens. But it’s often very hard to know when those changes are going to happen.
Another example of the input changing is a shift in the mix of pitches a pitcher will use. Read the rest of this entry »