One of the reasons I've always been frustrated by the eight+pitchers all time teams is the absence of the backup catcher. Such rosters may include a couple of starting pitchers and maybe a reliever or three (and maybe even a couple of bench bats), but who warms up the relievers? It gets even better as the rosters begin to include full rotations and reasonable bullpens. Then, it's plausible that the pitching staff can cover a full season and it's not beyond the realm of possibility that all seven nonbattery players could manage a 154 or even 162 game season.
But nobody is going to catch 162* games in a season. Nobody who wants to actually use their legs in the future, anyway. Catching is gruelling, body destroying work and catchers are largely underappreciated by baseball fandom. Anything roster claiming to be a baseball team ought to have a backup catcher.
*The highest is 160, caught by Randy Hundley in 1968. In 1944, Ray Mueller and Frankie Hayes caught all 155 of their team's games.
I figure that 32 starts is a good estimate for a backup's playing time. Of course, a defensively oriented backup might be brought in as a late inning replacement (Yadier Molina in for Mike Piazza sort of thing) and a gifted bat could expect to see time as a pinch hitter or maybe even DH given a perfect storm of injuries. I estimate a light hitting backup might see about 150 plate appearances (though with the difficulty of getting my line up out, it might be noticably more), and a heavy hitter
Selection Joe Mauer
Despite his merely average 2011 and his mysterious weak leg disease, Mauer has returned to form as an excellent offense first catcher with apparently decent defense. (Catcher defense is notoriously hard to quantify). He's averaged just under 5 fWAR as season for the past 8. His batting like is strong: .322/.403/.468/132 (avg/obp/slg/wRC+). And Mauer has had a high peak so far, hitting .365/.444/.587/170 in 2009, good for a 7.9 fWAR season and an MVP.
While Mauer isn't much of a home run threat, he's 22.8% line drive rate is exceptional.* A high contact/high OBP line drive lefty, Mauer makes an excellent lefty bench bat when he's not starting at catcher. His OBP is main driver in this selection, as the power in the rest of the line up drives up to the value of getting on base. Mauer's handedness is a big part of the reason I picked him, as not only could I use a lefty on the bench, my starter selection is right handed, so I can pick starter off days to gain platoon advantage.
* Damn, I wish we knew Stan Musial's line drive rate. Let's set the over/under at 30%. I'll take over.
The obvious choice for the more defensively minded backup, our still rudimentary estimators of catcher defensive value peg Pudge as the greatest defensive catcher of all time with something like 166 runs saved above average. His caught stealing rate for his career is an impressive 45.68%. His defensive reputation and career batting line .296/.334/.464/104 belie his considerable batting peak, with his best qualifying season being 2004's .334/.383/.510/134. His durability was also exceptional: 2348 games started at catcher (most all time), 7 at first base and one a second base (where he had 1 put out).*
*For the 2006 Tigers. Presuming Brandon Inge was at third, one wonders if Jim Leyland could've swung an "all catcher infield".
Eventual Hall of Famer (and owner of a career 73.9 fWAR) Rodiguez's big weakness was lack of plate discipline, with only a 5.0% walk rate. Even so, he's an excellent pick, with unprecendented durability, elite defense and a strong bat, he's just not the best fit for my line up.
Cochrane profiles a lot like Joe Mauer, but from the pre-integration era (points off) and without the 170 wRC+ season. A good choice, particularly if love you OBP (and I do).
A power bat
If you prefer that your backup catcher be a huge bat of the bench, even if he's (relatively) defensively weak, Mike Piazza makes a good choice. Life time .308/.377/.545/140 is great line for anybody, with a fantastic peak in 1997 of .362/.431/.638/183. Then again, he's a righty, doesn't quite match Mauer on OBP (I conject I'll have plenty of power either way, I'll take saving my outs) and you might want to take Jimmie Foxx, anyway. Only 108 games at catcher across his career, we know at least that he was familiar with the position and astronomical (though again pre-integration) career batting line of .325/.428/.609/159. Josh Gibson, too deserves a mention.
In many ways, the opposite of all of the other options, Molina seems a strange pick. A career batting line of .238/.286/.342/66 and a career fWAR of 4.7 make him appear, in some ways, to be the canonical backup catcher, Molina actually can be justified as an avant garde choice. It seems that Molina's hidden value lies in his ability to frame pitches. The Rays certainly think so, as his current .196/.278/.309/67 batting line isn't very enticing. From the Mike Fast's linked article:
Catchers appear to have a substantial impact on the success of their pitchers through their ability to gain extra strike calls from the umpire. This is an important factor to consider when valuing the contributions of catchers to a team. We have identified at least two specific techniques that affect catcher performance in this arena. Given the important impact on major-league teams, further research along that line is warranted.
Fast estimates that Molina's pitch framing ability is worth about 35 runs above average per 120 games caught. That's substational (and shows how much more work needs to be done on catcher defense, as that outweighs all of the components of catcher defense that we do account for by a signficant margin). That comes .032 runs per inning saved above average.
So, if you're an uncaring manager who cares not for your starter's knees or needs, or you just like he can take it, you could use your starter or maybe your utility player for nearly every regular season start and use Molina as a late inning shutdown catcher. Assuming he averaged 2.0 innings of catcher relief per game for, say, 150 games, that's worth about 9.7 runs above average defense (roughly an extra win across a season) and hopefully keeps his lousy bat out of the lineup. Given the higher leverage of late situations, that significant improvement to pitching performance that Molina provides could actually be worth more. Just warm him up with the shutdown reliever and play "Hells Bells" as your shutdown battery takes the field.
The pitchers might love it, too. Even for Marianno Rivera, the difference between Jose Molina and a league average catcher is 0.29 ERA, which would put him at 1.92 ERA (and presumably lower his FIP by the same, given that pitch framing largely effects strike outs and walks).*
*So what's the difference between Jorge Posada, an apparently bad pitch framer, and Jose Molina, a great pitcher framer on Rivera's ERA? Calculate Rivera's Earned runs per inning, Posada and Molina's Pitch Framing runs saved per inning from Fast's data and determine their difference. Subtract that difference (or rather it's absolute value) from Rivera's ER per inning and multiply by nine. I get 1.50. A lifetime ERA of 1.50. High leverage, shutdown catchers (or rather shutdown batteries) are either the wave of the future or the impetus for the next sea change in baseball with automated strike calling. You read it here first.
Jose Molina, so damn crazy, it just might work.