One of the Yankees’ obvious weaknesses this season is their defense behind the plate. Jorge Posada has long been a butcher back there, and even though Frankie Cervelli was voted as the organization’s best defensive catcher several years in a row by Baseball America, extended playing time in 2010 has exposed him as no better than average defensively. At least for now, I mean, he could always improve with more reps and experience.

Posada has thrown out just 19% of attempted basestealers this year, Cervelli even less at 14%, and that’s just part of it. The passed balls have allowed countless runners move up, and there’s no better example of it than this game against the Mariners two weeks ago. Posada allowed two runners to move up on a passed ball in the 8th inning, and one pitch later a two run single tied the game. While not completely responsible for the blown lead, the defensive miscue was certainly a big factor.

Considering how much we’ve talked about catcher’s defense this year, I wanted to try and come up with an actual number for how many runs the Yanks’ backstops have cost them defensively this season. Because there are so many immeasurables when to comes to catcher’s defense, we’re going to have to stick with the basics: stolen bases, caught stealings, wild pitches, and passed balls. Of course this isn’t perfect, because it’s not just catchers that factor into those four stats, pitchers have a say as well. The broad assumption in this analysis is that the pitcher’s effect will even out when looking at the 30 teams across the first half of the season.

Stolen bases and caught stealings are nice and easy to understand, a guy either successfully stole a base or he didn’t. There’s a little more of a gray area with wild pitches and passed balls because official scorers and their sometimes questionable decisions come into play, and there are certainly wild pitches that a catcher doesn’t even have a chance to make a play on (say a pitch over everyone’s head to the backstop). I’m looking at it in a bottom line kinda way, did the catcher stop the ball or not? Good catchers will still stop a fair share of would-be wild pitches, and even then we’ll assume the number of plays a backstop had no chance on will even out given the sample.

I tallied up each teams total in the four stat categories for the 2010 season, then assigned run values to each event based on The Book. Defensively, a stolen base against costs a team 0.16 runs, but throwing a runner out trying to steal saves 0.45 runs. You don’t need to be a sabermetric whiz to understand that losing a baserunner hurts a team more than moving one up 90 feet helps. Wild pitches cost 0.26 runs, passed balls 0.28. It makes sense that those two are close in value, since they’re basically the same thing with two different names. I turned everything into a rate stat for comparison purposes, arbitrarily selecting 180 innings as my unit of time (20 games).

The big league average is exactly two runs lost defensively per 180 innings, which passes the sniff test because it’s tough for a catcher to prevent runs in this analysis. He’d have to throw out a ton of runners to actually save runs, which just isn’t realistic. It basically comes down to who gives up the fewest runs. The AL average is 2.2 runs lost, the NL 1.9. I ran the numbers just to see if the small ball NL approach had a big impact in the numbers, but it’s good to see that they’re close. I’m going to use ML average for the rest of the post.

You can see my entire table of results here. The table’s too big to embed, so just click the link if you want to see the full breakdown by team. My fancy acronym for this stat is cRSAA/180, which stands for catcher’s runs saved above average per 180 innings. Yes, I just wanted a nerdy name, so sue me. All I did was figure out how many total runs a team lost defensively per 180 innings, and compared it to that 2.0 ML average. The Cardinals have the game’s best defensive catching corps, saving 1.9 runs above the league average per 180 innings. This passes the sniff test because Yadier Molina has a reputation as a studly defensive backstop. The Diamondbacks are on the other end of the spectrum at 2.4 runs below average. Apparently they’re bad at everything.

The Yankees came in at 1.4 runs below average, tied for fourth worst in the game. The only teams below them are the D-Backs, Pirates (-1.6 cRCAA/180) and Angels (-1.5), and they were tied with both the Giants and Red Sox. Over a 162 game season, assuming nine inning games, the Yanks’ catchers will cost them 11.34 runs defensively, which is basically one win. For comparison’s sake, St. Louis would pick up a win and half because of their catcher’s defense, Arizona would lose another two games. The different between the best and worst teams is three and a half wins, hardly insignificant.

It probably didn’t surprise you that the Yanks came in towards the bottom of the pack, or at least it shouldn’t have. Let’s break it down individually for Posada and Cervelli…

First of all, apologies to Chad Moeller. Secondly, as you can see neither Posada or Cervelli are assets on defense. Posada has cost the team 1.8 runs below average with his glove for every 180 innings he’s caught this year, Cervelli a touch less at 1.1. If Posada were to catch 120 nine inning games, his defense would cost the team 10.8 runs, or one win. Of course his offense, even at 2010 levels, would provide just over 17 runs, so the next gain is six runs, for all intents and purposes.

Cervelli, on the other hand, would cost the team 6.6 runs below average if he played 120 nine inning games, and his bat would also be another 7.4 runs below average assuming 2010 levels of production. All told, the Yankees would be 14 runs in the red with Cervelli as their starting catcher compared to six runs in the black with Posada. It’s a 20 run difference, two wins in a tight AL East. This assumes a set designated hitter and that only one of the two catchers play per game.

Yes, this is an extremely oversimplified way of looking at things. There are parts of catcher’s defense that we can’t even begin to quantify, but the information we do have tells us that the Yanks’ catchers are hurting them with the glove. Posada mitigates all of that damage with his stick, Cervelli not so much. He’s supposed to be just a backup though, so in theory it shouldn’t hurt as much. You expect those guys to be below average. The real problem is that Cervelli has had to play so much this season that both his bat and glove have become detriments to the team in a very real way.

Catching issues are hard to hide just because of the nature of the game. The catcher is in on every play, every pitch. The demands of the position are so extraordinary that most of the time you’re just looking for the least harmful option. You don’t expect offense, you just hope for something more than complete incompetence.  The Yankees’ catchers are holding them back a bit this year, but their pitching and offense is good enough to more than make up that lost win in the standings.