During spring training, Roy Oswalt was asked which catcher he preferred to throw to--Jason Castro or J.R. Towles? Oswalt took perhaps a diplomatic approach, so as to not select one teammate over another, and answered that his favorite catcher is in Los Angeles. This was an obvious reference to Brad Ausmus; and Oswalt is not the only Astros' pitcher to say that about Ausmus--notably Andy Pettitte and Roger Clemens were entranced with Ausmus' receiving ability.
The notion of catcher "intangibles" has been viewed with considerable skepticism in the sabermetric community. The very term implies that it is unmeasurable, or at least difficult to measure. So, it's not surprising that people who are devoted to measurement would be skeptical. And this is particularly true when teams give jobs to catchers with poor offensive skills (such as Ausmus) based on intangibles. But you probably would have a hard time convincing pitchers to share the skepticism. Think about the fact that some great pitchers brought their own caddy with them as they changed teams; an example of this is Greg Maddux.
Recently some sabermetric studies have addressed the intangible issue, with surprising (perhaps controversial) results; results which say that Oswalt and other pitchers knew something about the existence of mystical catcher traits. This study (Bill Letson) at Beyond the Boxscore uses pitch f/x data to analyze catcher pitch framing ability. In effect, the study attempts to quantify the "extra" strikes which a catcher can induce from the umpire. In discussing this study, I would suggest that we define "pitch framing" rather broadly. The skill could include knowledge of individual umpire strike zones, the ability to quickly determine the available strikes in an umpire's zone as the game progresses, ability to determine which type of pitches are most likely to be called strikes, as well as the normal definition of "framing," in terms of giving the appearance that a close pitch is in the strike zone. If you realize that this information processing has to be combined with the other things a catcher has to know (hitters' weaknesses, pitchers' strengths, pitch calling sequence, etc.), the catcher has a lot to think about. One would imagine that catcher experience is an important to the catcher's ability to process all of these factors.
The study's conclusion, supporting a hypothesis that catchers can induce extra strikes, is less surprising than the quantified result. The difference between worst and best catchers was over 10 wins per season, which is really high. The sheer size of this differential raised skepticism (which you can read in the comments on the article). It's worth pointing out that other studies have shown similar large values. But, even if the quantification turns out to be an overstatement, the existence of the impact is significant. In case you are interested, Brad Ausmus seemingly has the ability to induce extra strikes, whether in LA or Houston, to the tune of reducing pitchers' ERA by .05 to .08, or approximately 1 win per 120 games. Both J.R. Towles and Quintero are below average in framing results, with each raising pitchers' ERA by about .05. Obviously, the pitcher has a role in this effect, since a pitch can't be framed unless the pitcher can come close to hitting the catcher's target. So, the study's data shows battery pairings too; but, frankly, the sample sizes become so small for these splits that I didn't pay much attention to it. However, a google doc is available to be downloaded with the article.
Another important catcher skill is blocking pitches in the dirt. Pitch f/x provides a greater ability to measure this skill. A 2008 study, based on Gameday data as far back as 2005, shows historical information on pitch blocking skills. Brad Ausmus is very good at this, which is no surprise to Astros' fans. Brad Ausmus edges out Yadier Molina as the best catcher at blocking pitches, 2005 - 2007, with +13.61 runs over the three year period. Pudge Rodriguez is the worst at blocking pitches over the three year period.
Beyond the Boxscore has a recent study which attempts to project 2010 catcher performance in blocking pitches, based on historic data. This surprise me a bit: the Astros' own Humberto Quintero is projected to be the second best catcher at blocking pitches in 2010 (+4.18 runs/120 games), behind Jason Varitek. J.R. Towles apparently didn't have a sufficient sample size to warrant a projection. Since Towles appears to be good at blocking pitches, I would be interested in his projection in the future. Combined with Quintero's good arm, this would appear to support the idea that Quintero provides some decent value as a back up, even if he is a liability in the batter's box and on the base paths (home run in last night's game, notwithstanding).
Of course, we don't know how Jason Castro will measure out on these metrics. We know that he has a reputation as a good defensive catcher; so I would assume that he also will be good at blocking pitches. Castro's framing ability is an unknown. If you accept the broad view of the term I described earlier, my guess is that Castro will take time to develop the experience necessary to giving his pitchers extra strikes. As noted above, neither Quintero or Towles are particularly well developed on this skill.
As an aside, I am amused at the frequent comments on Chron.com blogs from fans demanding that Towles should be cut and Castro handed the ML starting job right now. Fans are almost always making their suggestions based only on players' perceived offensive results; and seldom do they consider these less measurable defensive/intangibles skills. But I doubt that these fans have looked at Castro's minor league current offensive stats, or else they would realize that he hasn't exactly made his case as a better offensive player than Towles. With a .216 average, no extra base hits, and a .586 OPS against AAA pitchers, Castro is struggling at the plate. Some of this may be bad luck (low BABIP), but Castro may take some time at Round Rock this year to develop into a major league catcher.
As I conclude my discussion of the catcher studies, I should point to an outgrowth of those analyses which finds that a ballpark effect exists for strikes. This study at Beyond the Boxscore emanated from attempts at replicating the catcher framing analyses. In the course of that work, the author investigated the pattern of strike calls by ballpark. Using false strikes and false balls (i.e., pitch f/x says the umpire's call is wrong) by ballpark, the study found a distinct differential by ballpark which often extended over more than one year. Minute Maid Park had more false strikes than average in 2009, but less in 2007 and 2008. The author wondered what ballpark characteristics could cause ballparks to affect strike calls. Possibilities include umpire assignments which are inadvertently systematically biased, lighting conditions, or hitting backgrounds which affect the umpire's depth perception. However, the author leans toward one possible explanation which could be bad news for those of us who rely on pitch f/x: the f/x data may be inaccurate, due to configuration of cameras in each ballpark.
If you've made it this far--and I fear that some may find this subject matter boring--what are your thoughts on the Astros' catching situation. Zachary Levine's blog at the Chronicle makes a big deal out of the perception that the Astros do not have a starting catcher. I'm not sure this is important. Should the Astros have a starting catcher? Who should it be?