from Amazon
Tuesday, July 24, 2007
Forecasting Pitchers
Building on the work I previously released, here is some more data:
This is all pitchers
- born between 1957 and 1974
- aged 25 to 28
I put each pitcher in one of seven experience classes.
Experience n 25-28 29-32 rate Wins 1 36 3,745 2,832 76% 0.582 2 72 2,988 2,137 72% 0.521 3 108 2,105 1,553 74% 0.502 4 144 1,403 903 64% 0.474 5 180 912 628 69% 0.474 6 216 499 474 95% 0.462 7 611 123 131 106% 0.398
The first line read like this: I take the 36 pitchers who faced the most batters at age 25-28. They average 3745 batters faced per pitcher. At age 29-32, they averaged 2832 batters each. That age 29-32 number is 76% of the age 25-28 number. They had a .582 W/L record.
The second line are the next 72 pitchers with the most batters faced at age 25-28.
For the first 5 lines, which comprises of the 540 most experienced pitchers (which is at least 695 batters faced over 4 years), they are all at the 70-75% rate.
As you can see by the wins column, the quality tracks the experience, though this is hardly a surprise.
(For you replacement-level fans, note that the win % for the last group of pitchers, the scrubs, is .398, which can be compared to the W/L record of their teammates of .484. On a neutral team, that .398 adjusts as .408. This is further evidence that the replacement-level for pitching is indeed .410. This would breakdown as .380 for starters and .470 for relievers.)
Overall, the number of batters faced at age 29-32 is 75% of the total faced at age 25-28, give or take 100 batters faced, for each experience level.
So, forget about how many batters they did face. Forget how good a pitcher he is. The short-rule to forecasting a pitcher’s future IP (for these age classes) is simply to reduce his actual batters faced by 25% over that time period.
An annual 11% drop achieves this. So if you have a pitcher with 3000 batters faced at ages 25-28, his next 4 years will be roughly: 668, 594, 529, 471 for a total of 2261 batters faced at ages 29-32.
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By the way, the Marcel rule is to use 50% of the previous year, and 10% of two years ago, plus 200 batters faced. This also works quite well.
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Also note that if I looked at all pitchers born since 1884, their age 29-32 batters faced is 27% fewer than their age 25-28 batters faced. In short, historically speaking, we’re not seeing much change.