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May 17, 2003

The Catcher Arms Race

What the Intimidation Factor Means for Catcher Defense

by Michael Wolverton

A few items from the mailbag generated by The Man With the Golden Gun: 2002, which ranked baseball's best catcher arms using a measure of Stolen Base Runs Prevented (SBRP):

I was glad that you concede that your analysis is biased against players that have a solid reputation. It strikes me as a limited phenomenon anyway. Only the real newbies are likely to get much of a bump from extra throwing opportunities against uninformed opposition. All catchers with good reputations will benefit by the comparison to the Piazzas of the world who have so many attempts against them.

-- CDS

I did note in the original article that a catcher's reputation influences the number of steal attempts against him, and that the number of steal attempts in turn affects his Stolen Base Runs Prevented rating. But I wouldn't say the analysis is biased against players that have a solid reputation.

It all comes down to what you're trying to measure, skill or value. If you're trying to measure skill--how strong, accurate, and generally impressive a catcher's arm is--then yes, you would want to give extra credit to those catchers who prevent runners from even attempting to steal. But SBRP is trying to measure value--how many runs the catcher prevents the opposition from scoring through his control of the running game. And if run prevention is what you're after, shutting down steal attempts isn't necessarily a good thing. In fact, you could make a strong case that it's a bad thing.

That's because steal attempts seem to be a net negative for offenses league-wide. (I'll say in a minute why I have to use the qualified "seem to be.") On average, a stolen base is worth only .16 runs to the offense, but a caught stealing costs the offense .49 runs. (Those numbers come from the work I did, but other people have come up with similar values.) That means that running teams need to succeed about three times (.49/.16 = 3.1) for every time caught stealing just to break even in the running game.

But major league teams don't come anywhere near that break-even rate on the basepaths, coming much closer to two successful steals for every caught stealing than three. Last year major leaguers stole 2750 bases and were caught 1282 times, for a success rate of 68%. (Contrary to popular belief, the numbers don't differ much between the AL and the NL.) Also, major league runners stumbled into 330 pickoffs, many of which involved would-be basestealers leaning the wrong way. Add it all together with the run values above, and you get that the running game cost major league offenses a total of 350 runs last year.