April 1, 2002
Aim For The Head
Innings Pitched to Wins
I recently found an article from last season by Joe Morgan that I don't quite understand.
Thanks for writing, A.F.
Morgan actually does make sense here because it's the rate of wins per inning that really counts. Let me try to explain with an example:
In 2001, Jay Witasick went 5-2 with the Padres in 38 2/3 innings, or a win every 7.73 innings. His teammate, Brian Tollberg, went 10-4 in 117 1/3 innings, or a win every 11.73 innings. As you can see, Witasick was much more efficient at converting innings to wins. In fact, at that rate, he'd have had the same record as Tollberg in 77 1/3 innings, versus the 117 1/3 that Tollberg needed. Give Witasick the same number of innings as Tollberg, and you'd expect him to win 15.2 games--call it 15 wins--versus 10 wins for Tollberg in the same number of innings.
Now, five wins may not sound like a lot, but it has a big effect when you project it across the entire staff. If every pitcher on the Padres was as efficient in converting innings to wins as Witasick, they'd have won 186 games last year. That's unrealistic, of course, because you can't assume that they'd all continue at this rate (even Witasick dropped to a win every 13.4 innings after being traded to the Yankees), so knock, say, a third off that total to get something more reasonable.
Anyway, that's why you can't ignore the effect that innings pitched has on wins. You can, on the other hand, ignore ERA because you've already accounted for it by counting wins, since by definition, you score more runs in a win than you allow. Using ERA would be double counting.
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Keith Woolner is an author of Baseball Prospectus. You can contact him by clicking here.