An Attempt to Capture Catcher Defense

A couple of weeks ago I put something together over at VEB about catcher defense in the NL at the All-Star break and was invited to extend my analysis to all major league catchers over here. As we all know, the impact of catcher defense is very difficult to quantify. Even Fangraphs has a difficult time with it, since it uses UZR to evaluate defense at every other position on the field. Just looking at its list of qualifying catchers, only Victor Martinez and Yadier Molina ostensibly receive any value from their defense whatsoever – and that comes from the time they’ve each spent at first base.

It’s not true, of course, that catchers have no defensive value. We do know, from The Book that a catcher’s ability to throw runners out attempting to steal has value and that his inability to do so detracts from that value. The Book tells us that a stolen base is worth 0.175 runs and a caught stealing is worth minus 0.467 runs. We also know that wild pitches and passed balls are worth approximately 0.27 runs as well. Using those run expectancies, I’ve taken the catcher on each team who has garnered the most playing time behind the plate and figured out how many runs each caught stealing has added to his team and how many runs each stolen base, passed ball, and wild pitch has subtracted from his team.

The CS% and WP+PB/G don’t tell the entire story, however. There has to be some value in a catcher’s reputation’s ability to prevent other teams from even attempting to steal a base. Is Bengie Molina really more valuable than Yadier b/c he’s thrown out 20 runners in 84 attempts while Yadi’s only thrown out 14 of 37? Why should catchers with reputations that prevent teams from attempting to steal be punished? I figured that the value of a catcher’s reputation is equal to the value of a stolen base times the likelihood that the runner will get caught times the number of times runners have forgone the opportunity to steal b/c of the catcher’s reputation. In other words, I figured the average number of stolen base attempts per catcher game (0.869) and determined each catcher’s expected stolen base attempts based on his number of games played. I then subtracted his actual stolen base attempts from the expected number and multiplied it times the run value of the SB (0.175) times the likelihood the runner would be caught stealing (CS%). If a catcher had more SB attempts than expected, he has the reputation of being easy to run against and if a catcher had fewer SB attempts than expected, it’s b/c his reputation prevented base runners from attempting the steal. I called this number Rep runs.

I then added BR runs, Miss Runs, and Rep Runs together to determine the total runs scored against a catcher on the basis of his inability to stop balls in the dirt or prevent runners from stealing a base. Then, as UZR does, I computed the total runs on a 150 game basis in order to level the playing field. Perhaps 150 games isn’t the right number to use since catchers almost never play 150 games, but it allows us to compare them and squares it w/ UZR. I then figured the average and determined how many runs above or below average each catcher was, on a 150 game basis. The results are below:

This isn’t a perfect measure, of course, as pitchers bear at least some of the responsibility for wild pitches and stolen bases but it does try to capture the run value of the most important plays that catchers make. And I’ll add again that perhaps a 150 game measure isn’t the way to go but I’m not sure it’s clear what the standard should be. 130 games? If so, the runs above and below average would be closer to 0 than they are now but the ones at the top would still be at the top and Posada, Varitek, and Hundley would still be at the bottom. On the other hand, who'd have guessed Ryan Hanigan would be at the top of this list. Still, when you're throwing out nearly half of all potential base stealers, you're helping your team quite a bit.

I’m interested in whatever feedback you have to offer as I’m always trying to figure out ways to make this stuff more precise.