I wrote something up at Baseball Prospectus about pitch sequencing. This time, I scaled up the initial analysis I did before, wherein I just looked at Clayton Kershaw and Joe Saunders. In that limited sample, I found very little evidence of non-random sequencing for 2-pitch sequences.
For Baseball Prospectus, I examined all of the starting pitchers (>100 IP) using a similar approach, but applied to 3-pitch sequences (specifically, the three pitches which start an at-bat). I found these longer sequences to be much less random than 2-pitch sequences, and that variation in the level of randomness correlated with some elements of pitcher skill (see the article for more details). The results are largely uncertain at this early stage, but point in any case towards sequencing being important for pitchers (which was probably obvious before).
Many caveats apply, this analysis still being very young, so I won’t try to claim that I’ve solved sequencing or somesuch. However, I do think that, as with my earlier work using entropy, we can apply some cool tricks from information theory to figuring out how pitchers harness variation in their endless quest to confuse, befuddle, and out-think the batter.