Strasburg and PitchFx Pitch Types

As I was poking around at Stephen Strasburg’s most recent start in our pitchf/x pages, I noticed that MLBAM was classifying one of his pitches as a two-seam fastball, which I recall was not the case in his first start a week ago. So I went back to check his first start and low and behold, a number of his four-seamers had been reclassified to two-seamers (and a couple to curveballs changeups).

This correction seems to agree with the this note from J-Doug over at Beyond the Box Score:

*Note: Several commenters and analysts (such as Tim Kurkjian) have noted that Strasburg throws both a four-seamer and a two-seamer (or what Strasburg calls a ‘one-seamer’). This makes sense considering the break on his fastballs. However, MLBAM doesn’t yet have enough data (I assume) to separately classify these two pitches, so they both came through as four-seamers. I’m going to rely on MLBAM’s estimation for now, since that’s where the data came from, but feel free to read everything that is labeled “four-seamer” as just plain “fastball.”

And it also seems to match up pretty well with Nick Steiner’s own pitch classifications.

I don’t have anything in particular to note about the pitches that changed in classification, but it is important to note that pitchf/x data is retroactively updated as the pitch classifying algorithms are adjusted for each individual pitcher.