Question #1: Which is the more relevant shift, Zito's pitch repertoire or MLB's pitch classification algorithm?
A number of commenters suggested that the reported change in Barry Zito's pitch selection was due to changes in the Pitch FX algorithm rather than actual modifications by the pitcher. To test this, I needed to develop a (rather rough*) pitch classification scheme and apply it evenly to both seasons' data.
Having done so, I feel I can answer this question one of two ways. One possibility is that Zito is indeed pitching more two-seamers and curves this year. Another possibility is that the embattled Giants hurler is throwing the same 4-seamer, but it's coming in slower, breaking less vertically, and breaking more horizontally--and he's still throwing more curves.
See the charts below (data from Brooks Baseball's PitchFX Tool):
Continue reading at BtB...