Why Do We Worry About Innings More than Pitch Counts?

As some of you know, I'm in the middle of reading Baseball Between the Numbers. It's a very interesting read, even though some of the statistics themselves go over my head. Still, I understand the theory, and some of the authors' findings interest me.

One such was their very simple conclusion that throwing a lot of innings doesn't necessarily increase injury risk, but doing so while fatigued does.

The chapter in which that is such discussed argues that there's really no decent reason not to go to a four man rotation, and that the last team to really try it--the 1995 Royals--failed not because the pitchers threw too many innings but because they threw too many pitches in the games they did throw.

Pitching outings, they say, can be divided into four categories based on how many pitches that the starter has thrown, with more pitches meaning more fatigue and an increased injury risk.

Now, as you know, many young pitchers are tracked by the innings--not the total pitches--that the pitcher has thrown. The Verducci Effect, which has been discussed here before, uses innings as the theory's measure.

However, using innings as a measure here is misleading. There is, for example, a huge difference between pitching nine or ten-pitch innings and thirty-pitch innings. Roy Halladay typically throws so many complete games because he keeps his pitch count so low.

Even more, even just using pitches themselves as a measure is misleading.

A pitch thrown with two out and the bases empty is highly different than a pitch thrown with, say, second and third and no one out in a tie game. It's different in terms of stress, in terms of positioning, and in terms of mental fatigue.

Imagine Joba Chamberlain's performance last night, constantly pitching out of jams, and contrast that to CC Sabathia or AJ Burnett pitching against the New York Mets.

Sabathia and Burnett are throwing more innings, and certainly in Sabathia's case more pitches, but because Chamberlain is throwing higher-stress innings, he is fatigued and rendered ineffective much earlier.

Concepts like the Verducci Effect certainly have proved themselves to have enough merit to be taken seriously, but one has to wonder if perhaps there are ways to improve on the theory.

What's more dangerous for, say, Joba Chamberlain? Is it him throwing 160 innings alone? Once again, a Roy Halladay 160 innings is not the same as a Joba Chamberlain 160 innings.

Just some food for thought.