Catchers are largely indistinguishable on defense and contribute only modestly to a team's offense. Obsessing over catchers is basically unhealthy--they fulfill a basic need of the game (to catch the ball from the pitcher) but in general are less important to a team's final win talley than a solid closer or pair of relievers in the bullpen.
Since the head-explode-de-jour is the purchase of Mr. Traenor for some sum that is less than the team's bat and ball budget for the year I figured it was a good time to put together an analysis of just how much--or how little--catchers contribute offensively to success. To do this I pulled the total catcher line for each team in 2010 from Fangraphs.
Slash totals plus wOBA for playoff teams:
Slash totals plus wOBA for non-playoff teams:
I then pulled the WAR statistics and removed the positional adjustment and replacement adjustment (since all catchers receive those) to examine how many runs good catchers can actually contribute in offense and defense.
For the eight playoff teams, catchers contributed on average 0.6 wins over the course of the season. This ranged from the Braves (whose catchers contributed 3.1 wins) to the Rangers (whose catchers cost 3.1) wins. For the non-playoff teams, catchers cost on average 1.2 wins, ranging from a positive contrubution of 0.3 wins (Blue Jays) to a cost of 3.1 wins (Mariners). No catcher's contribution was decisive in deciding a playoff berth (the closest was the 0.7 wins generated by the Giants catchers over the Padres).
The majority of value contributed by a catcher is from offense. The six playoff teams generated average total of 0.7 marginal wins due to the offensive contributions of their catchers (six of the eight were positive). The non-playoff catchers cost their teams a net total of 1.1 wins on offense. There are also a significant number of catchers who suck offensively--two sets of catchers cost over 3 wins on offense (Mariners, Astros), six cost over two wins (Rangers, Marlins, Royals, Tigers, Nationals, Pirates), and three more cost over a win on offense (Orioles, Mets, Athletics)
The two groups are virtually the same in defense--playoff teams had catchers who cost their teams 0.7 wins due to defense, non-playoff catchers cost their teams 0.8 wins on defense. No team had catchers worth over a win defensively (the Rockies were close at 0.9 wins) while only two teams had catchers who cost more than a win defensively (the Pirates at a cost of 1.3 games and the playoff Yankees at a 1.1 cost).
To put this into perspective: the best catchers (the Brave's Brian McCann) contributed 3.1 wins. The next best catching combos contributed a win and a half.
Joakim Soria was worth more last year than any team's catchers except the Baves.
Tejeda and Farnsworth (during his Royals tenure) were worth the same as the #2 and #3 catching combos.
Greinke + Hochevar contributed more wins than all catchers from all playoff teams combined.
Someone has to catch the ball from the pitcher. Thus we have catchers. They're all basically interchangeable defensively. The best you can reasonably hope for on offense is an additional game on offense while the worst will cost you two to three games.