Already in his brief career, Mauer has accumulated an impressive WAR of 40.3 (entering 2012), with three seasons of 7.0 or above. He’s the only catcher in baseball history with three seasons at 7.0 or higher, and only Campanella, Bench, and Piazza had as many as two. Given that Mauer is just 28 as of 2012, that gives him an excellent chance to lay claim to having the best peak of any catcher, at least with the bat.
It remains to be seen how long he’ll stick behind the plate, though. He’s certainly not a Fisk or a Boone or a Pudge – a catcher who can squat back there for 1,700+ games. Mauer will flip down to first base or be moved to the corner outfield spot at some point, probably by the time he’s 32 or 33. But he’ll still have 1,200 or so games on his resume as a catcher.