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Monday, October 06, 2008
Power or Finesse Pitchers in the Post-season?
Bill James, in what will surely be an article to appear in the next Gold Mine, looks at the issue of whether the Power or Finesse pitchers perform better in the post-season. He does his typically enjoyable study of matched pairs, where he proceeds to select 100 power pitchers and 100 finesse pitchers (they match in a variety of ways, except in K and BB). They match up quite well in the categories he selected. He also notes:
But the power pitchers had averaged 183 strikeouts, 76 walks; the finesse pitchers had averaged 107 strikeouts, 57 walks. The two groups were nearly even in terms of home runs allowed (a few more for the power pitchers), but the finesse pitchers had given up, on average, 18 more hits. 18 more hits, 19 less walks, one less homer. . .the same results overall.
As you guys know, I’m big on simply doing K minus BB, per PA. And just looking at the bolded part, you can see that I think the two groups are biased. I responded:
Very enjoyable study.
If you look at the BABIP (batting average on balls in play, or H minus HR divided by PA minus BB, K, HBP, HR), I think you will find that the finesse pitchers ended up with a BABIP of 10 or 12 points better. Or, probably a bit more lucky than the power pitchers that year. So, I think the study is biased in that while the component ERA may come out as equal for the two groups, the component ERA of the power pitchers is more indicative of the true talent.
I estimate that the 10-12 estimated difference in BABIP to be roughly worth 0.20-0.30 in ERA, thereby giving you a perfect match for the post-season difference.
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We can even try to estimate FIP, and I get a 38 point difference, in favor of the K pitchers. So, I don’t think that we really have a matched pair of pitchers here. The idea behind matched pairs is that you can match on everything, except the thing you are looking at. And the plan is to make sure not to bias the two groups. But, I think Bill does have a biased group of pitchers. The FIPs aren’t close to matching, the BABIP don’t match, and what is more indicative in the future is a pitcher’s FIP not his ERA. And his BABIP is the least indicative, but it makes up a substantial part of ERA, one of James’ indicators.
In any case, I really enjoyed the study, and it would be an ideal study by simply introducing one extra parameter (FIP or BABIP) into the equation.