Phyllis Schlafly: Not happy with Win-Loss, either.

In a fascinating bit of hot stove nerdery, Nick Steiner at Hardball Times uncovers a new possible weakness in the ERA statistic in an innovative, defense-independent way.  Long story short, he took AJ Burnett’s ten best 2009 outings (average outing: 1.06) and ten worst (average outing: 9.13) then looked at his stuff, location and pitch selection and found that AJ throws just about exactly the same when he’s getting shelled as when he’s dealing.

In his 10 best starts, he averaged a Game Score of 70.9. In his 10 worst starts, he averaged a Game Score of 31.9. More intuitively, his ERA was 1.06 in his good starts compared to 9.13 in his bad starts… quite the difference.

I then grabbed all of the PITCHf/x information on those two groups of starts. In case you are unfamiliar with it, PITCHf/x is a ball- tracking technology powered by SportVision, which measures certain key characteristics of each pitched ball, including speed, spin deflection (movement) and location. After manually classifying Burnett’s pitches game-by-game (yes this was a pain), I was ready to look at the data.

My agenda was simple. I wanted to see, using the intrinsic qualities of each pitch, exactly how differently he pitched in his best and worst starts of the season. I looked at three variables: stuff, location and approach.

…[I] found no meaningful differences in terms of what he threw, the velocity/movement of his pitches, where he threw them and when he threw them. I think I’ve established that there was practically no difference in how he pitched in his good starts compared to his bad starts.