Thursday, October 11, 2007

Tom Verducci's theory on overworking young pitchers

Tom Verducci says that if you give a young pitcher 30 more innings than he's ever pitched before, you're abusing him, and there's a good chance he'll get hurt, or "take a major step backward in [his] development."

How does he know? Anecdote, mostly. But he lists the six pitchers under-25 who qualified in 2005. Three of them (Liriano, Chacin, and Kazmir) got hurt, and the other three (Cain, Duke, and Maholm) saw their ERAs jump. (If those are really the only six pitchers who met the criteria, then I have to admit that's a pretty good anecdote.)

But still: does this criterion for the "year-after effect" really make sense? There are several reasons why it might not:

1. Regression to the mean. When a pitcher throws more innings than expected, it's probably because he's pitched better than before; it's hard to set a new high when you're giving up lots of runs in the early innings. And if your performance exceeds expectations, there's a very good chance it's because you were lucky. And so chances are you'll regress the next season. That has nothing to do with overwork or arm trouble, just luck.

2. Total Innings. A pitcher who exceeds his previous high by 30 IP is also likely to have thrown a good number of pitches. How does Verducci know it's the difference between this year and last that causes any effect? Maybe it's just the total number of pitches.

3. Season Length. Wouldn't you expect it to be harder on a pitcher's arm to set a new high in innings over, say, half a season, instead of over a full season? You'd be throwing more pitches per start, or more pitches over a shorter period of time. Suppose a manager reads Verducci, and notices that his pitcher is 29 IP over his previous high, even though it's only July. Should he really sit that young pitcher for three months? That doesn't make sense to me, but I'm not an expert. (Also, Verducci includes post-season innings. If that pitcher is 29 IP over at the end of the regular season, does Verducci really think those three extra playoff starts, on normal rest, are going to cause such a large problem?)

4. 30 innings doesn't seem like a lot. Thirty innings is about one inning per week. That doesn't seem like all that much. For a starter, it's about one inning per start, which perhaps is a lot – that one extra inning comes when the pitcher is somewhat tired. But if the starter set a new high, he's probably pitching well, which means he's giving up fewer hits, which means that he's not throwing as many more pitches as the 30 inning figure would suggest. That's especially true since managers are likely to limit young starters to a certain pitch count.

Anyway, this issue needs a real analysis, not just anecdotes. One way to study this question is to do paired comparisons. For instance, find two pitchers with similar ages and career statistics, but where one exceeded the 30 IP threshold, and the other did not. Does the less-experienced guy do worse later?

Or find two pitchers where both exceeded their innings by 30, but one is younger than the other. Does the young guy suffer more ill-effects than the old guy?

I'm betting that if you did a real study, you'd find any such effect is small – and, moreover, you find more of an effect using some measure other than "innings over previous high."

In any case, Verducci's article appeared last November. He listed pitchers in 2006 who met his criteria for possible problems. How did they do in 2007?

Cole Hamels: excellent year, better than last year
Justin Verlander: better than last year
Anibal Sanchez: shoulder injury
Jered Weaver: great 2006, regressed to mean in 2007
Sean Marshall: mediocre 2006, improved to mean in 2007
Scott Olsen: good 2006, bad 2007
Jeremy Bonderman: a little worse than expected in 2007
Adam Loewen: out with elbow injury
Anthony Reyes: equally mediocre both years
Scott Mathieson: injured in 2006
Boof Bonser: got a little worse in 2007
Chien-Ming Wang: exactly as good in 2007 as 2006
Rich Hill: improved a bit in 2007

Three injuries (two if you don't count Mathieson), maybe one collapse among the non-injured pitchers, and a few improvers. Make of that what you will.

Hat Tip:



At Friday, October 12, 2007 2:01:00 PM, Blogger Brian Burke said...

The "overuse" issue is a fertile topic in football, specifically with running backs.

Football Outsiders has proclaimed a "Curse of 370" in with RBs with over 370 carries in a year will breakdown the next year, either by injury or a fall-off in performance.

I've been trying to argue the concept of regression to the mean (your point #1) but it falls on deaf ears.

RBs with high numbers of carries are likely doing extremely well and on teams that are also doing extremely well. Because extremely good performances are extremely difficult to repeat by players and by teams, seasons following a high-carry years are naturally going to be less spectacular.

Also, the injury issue suffers from a severe self-selection bias. Since high-carry seasons *must* occur in non-injury years, the remaining years are going to show higher than average injury rates. I'm certain the same analysis applies to pitchers.

At Friday, October 12, 2007 2:05:00 PM, Blogger Phil Birnbaum said...

That's a good point about high-IP (or high-carry) seasons coming in non-injury years ... if Verducci did an actual study on this issue, that's one of the things you'd have to take into account.

Don't know how big it would be. Suppose 25% of all seasons have injuries, and 10% of all seasons are "high-carry". Then non-high-carry seasons would have .25/.9 = 27.8% injuries. Hey, that *is* fairly large. You'd see an 11% increase just because of selection bias.

Good call.

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