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February 15, 2002 Controlling the Running GameIs it the Catchers, or the Pitchers?"The Man With the Golden Gun", an article that ran last month on this site, recognized the most valuable and least valuable catcher arms in the majors last season. That piece generated a lot of reader response, including this email from M.H.:
I have my doubts about this Stolen Base Runs Prevented statistic. It seems to penalize catchers who are so good that the opponents don't run on them; you hint at that with the Ivan Rodriguez comment. Also, bases are stolen more on the pitcher than the catcher, aren't they? It is not clear to me that this statistic is telling you anything at all about the defensive abilities of catchers. Most of the email I received raised one or both the the two issues M.H. raised. Put more generally:
I'm going to save the first question for a later article, and focus here on the issue of the pitching staff's influence on a catcher's numbers. I'm not going to be talking about individual pitchers here. There's no doubt that the pitcher has a huge influence on the success or failure of a particular steal attempt, and it pretty much follows that an individual pitcher who's especially good (or bad) at keeping runners close can help (or hurt) the catcher's CS numbers during the innings he pitches. So catchers' caught stealing numbers must be measuring pitchers to a large extent, right? Not necessarily. The thing is, while one pitcher can make a difference when he's pitching, a catcher doesn't work with just one pitcher. Especially in today's game, where a fulltime catcher can handle a significant number of innings from ten or more different pitchers in a season, we might expect the runnerholding ability of the different pitchers on the staff to even out over the course of the year. How do we test this? We can start by checking whether catcher caughtstealing numbers tend to stay consistent from year to year. That is, do the catchers with the best CS numbers one year tend to be the best the next year, and are the worst one year also the worst the next? To answer that, we want to look at the correlation of catcher caught stealing from year to year. The correlation coefficient measures the strength of the relationship between two sets of numbers. Correlation coefficients range from 1 to 1. A correlation of 1 means the numbers are perfectly consistent, e.g., a high number one year means a high number the next year. A coefficient of 0 means there is no relationship between them at all. Here are the yeartoyear correlations of catcher caught stealing percentage for each consecutive pair of years for which I have data (minimum 50 stolen base attempts against each season):
Years Corr. Coeff. 19981999 +0.59 19992000 +0.57 20002001 +0.78 (I used CS% rather than Stolen Base Runs Prevented because CS%, as a rate stat, isn't measuring playing time. The correlations for SBRP are about the same for the years I checked.) Those are pretty high numbers. For comparison, the correlation coefficient for pitchers' ERA from 2000 to 2001 was +0.40, and for hitters' batting average those same years it was +0.48. The bottom line is that knowing a catcher's CS% from one year tells you a lot about what it's going to be the next year. That's some evidence that catcher caughtstealing numbers are measuring the catcher, but it isn't conclusive. After all, most catchers stay with the same team from one year to the next, and therefore you'd expect them to catch largely the same pitchers from year to year. Maybe the high correlations are just reflecting the high yeartoyear overlap in the pitchers a catcher handles. Maybe, except that there are an awful lot of examples, just from recent seasons, that seem to indicate that the catcher, not the pitching staff, plays the predominant role in generating the catcher's CS numbers. Here are just a few:
Those are just a few examples, but I've run across many others that are inconsistent with the "it's mostly the pitchers" theory. Of course, you could also probably come up with a few examples that would seem to support the theory. In fact, here's oneMike Matheny's throwing numbers took a big step forward when he joined the Cardinals two years ago:
Year SB CS CS% CPO SBRP Matheny MIL 1996 52 19 27% 2 1.8 Matheny MIL 1997 69 34 33% 5 7.9 Matheny MIL 1998 67 19 22% 0 1.6 Matheny TOR 1999 40 16 29% 0 1.3 Matheny STL 2000 44 46 51% 3 16.9 Matheny STL 2001 31 25 45% 5 9.7 These individual anecdotes are useful for helping us understand the issuenot to mention getting some actual baseball players into the discussionbut to really get at the question of the pitching staff's role in catcher CS numbers we need to return to looking at catchers as a group. We want to check correlations as before, but this time, to remove the potential doubts about the correlations shown above, we want to look at catchers who we know aren't catching the same pitchers from one season to the next. To do that, I looked at catchers that changed teams. I took all catchers who had at least 50 stolenbase attempts against them with two different teams during the past four seasons, and measured the correlation of their total CS% with the first team to their total CS% with the second team. (For those catchers who qualified with three teams, I grouped the first two teams into the "before" group and had their last team be the "after" group. I did it this way to make sure that the big Matheny jump mentioned above was included in the comparison.) The correlation coefficient for CS% from one team to the next was +0.53. That's still quite strong, and not a whole lot lower than the yeartoyear correlations for all catchers shown above. In other words, knowing a catcher's CS numbers with one set of pitchers tells you a lot about what they're going to be with another set of pitchers. The bottom line is that all the evidence that I've seen on this issue indicates that catcher caughtstealing numbers are measuring the catcher, without too much interference from the pitching staff. That doesn't mean it's impossible that there will occasionally be extreme pitching staffs that can have some positive or negative impact on a catcher's numbers, but it does mean that the next time a fan tries to defend his favorite catcher by blaming all his troubles with baserunners on his pitchers, you'd be wise to be skeptical. Michael Wolverton is an author of Baseball Prospectus. You can contact him by clicking here.
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