The Care and Feeding of Young Arms

With Kerry Wood in the headlines recently, there has been a lot of discussion in the press about how best to protect his (and other young pitcher's) arm. In May, Rob Neyer wrote a "Stats Class" column on the ESPN SportsZone site about the price pitchers ultimately pay when they rack up a lot of innings at a tender age. He looked at the 19 pitchers who have thrown 200 innings in a season since 1969 and compared their performance in seasons 1-3 with their performance in seasons 4-6. Here's what he found:

                      IP    K/9    ERA
    Years 1-3   11375    5.97   3.31
    Years 4-6    8565    6.24   3.43
     Pct. +/-   -24.7    +4.5   -3.6

He noted the large dropoff in innings pitches, gave a few examples (including Mark Fidrych) and concluded with:

You've heard a lot about Kerry Wood and Nolan Ryan. [snip] But there is one important difference between the two pitchers. Nolan Ryan didn't total 200-plus innings in a major-league season until he was 25 years old. No one ever talks about this, but it goes a long way toward explaining why Ryan was still throwing 90-plus fastballs two decades later.

Well, that got me interested in what a similar chart would look like for pitchers over the same period (1969-1991) who waited until they were 25 to pitch 200 or more innings. (I picked 1991 as the cutoff because it gave me six years of data to examine.) This list includes 54 pitchers and looks like this:

                    IP    K/9    ERA
     Years 1-3   31240   5.32   3.77
     Years 4-6   22448   5.44   3.81
      Pct. +/-   -28.1   +2.3   -1.1

So the innings pitched totals for the pitchers who saved themselves until their mid-twenties fell off even more than those who were rushed into action. And given that their performance over the second period was almost identical to the first, I'm assuming that their drop in innings pitched was primarily due to arm problems. Of course, it is possible that their teams expected them to get better and dumped them when they failed to improve. You could argue that we're talking about two different classes of pitchers here and you'd be right; pitchers with the ability to break into a starting rotation in their early twenties are as a group a lot more talented than those who come around four or five years later. Still, the differences in their ability should not have affected their susceptibility to arm woes.

By the way, I looked at a sampling of these pitchers, and with some exceptions (like Doyle Alexander), they did not exceed 200 innings pitched in the minors either.

Of course, I'm not recommending that it's okay for Kerry Wood to start throwing 150 pitches a game, or that it is somehow beneficial for a pitcher to top the 200 inning mark early. I guess my point is two-fold:

Innings pitched might not be the best measurement here. How many pitches he throws, especially when his arm is tired, is probably a better indicator than yearly innings pitched. Livian Hernandez pitched 96 innings in 1997 (not counting the post-season) and was probably overworked.
Pitchers' arms are fragile throughout their twenties. My guess is that the charts above wouldn't have changed that much (except for the number of pitchers involved) if I had picked 23, 27 or 29 as the target age. Pitching strategies are still evolving as we learn more and more about how to protect players from arm problems. It wouldn't surprise me if in a decade or so, most teams have six-man rotations and starting pitchers average from 150-175 innings a year. Of course then you'll have to listen to me complain about how they don't make pitchers like they use to. (Why in my day pitchers were men--tough guys who thought nothing of pitching seven, maybe eight innings on occasion-- especially if they had their good stuff, and the weather wasn't too hot or muggy.)

Tom Ruane

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