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Tuesday, July 29, 2008
Bronson Arroyo and pitching inside
Arroyo is having a very bad year of course, after being pretty successful for several years before that. Last I looked at my database, his ERA for this year was 5.97, his NERC was 5.95 and my own version of his DIPS ERA was 4.54. For NERC and my DIPS ERA, 4.00 is an average pitcher.
Anyway, according to Fangraphs and their BIS (not pitch f/x) data, his fastball velocity has been steadily declining, at least since 2005 (which is as far back as their data goes).
2005 89.5
2006 89.0
2007 88.4
2008 88.2
That is probably not too far from what is normal of a pitcher at his age, but it is still not good. However, I think his lack of success this year goes further than that, and I am proposing a theory. I would love it if one of the pitch f/x guys could check it out.
Alan Nathan, in that Corey Schwartz interview that we linked to in one of our recent threads, stated that from looking at the pitch f/x data, we can see that pitchers who throw hard can pitch inside successfully and that pitchers that do not cannot (pitch inside). He also mentioned that on an outside pitch, there is not that much difference between a hard thrower and a soft one, which is not really relevant to my discussion . All of that makes sense and is quite intuitive.
Anyhow, it appears to me from watching Arroyo pitch, that he likes to throw inside too much and that he does not have the fastball to do so. Maybe he could get away with that when he threw 90.5, but at 88.2, I don’t think he can. I think he has to stay almost exclusively outside. Also, maybe the movement on his fastball is not that conducive to throwing outside, so maybe with diminished velocity, he is just not that good of a pitcher anymore.
If you throw your fastball outside, I assume that you want more down and away movement.
I would love to see what kind of movement that Arroyo has on his fastball when he throws it inside as compared to other pitchers on inside pitches and I would love to see how often he throws his fastball inside as compared to pitchers with around the same velocity.
Any pitch f/x guys want to give it a shot? It might make for a good article!