Inspired by an interesting discussion over at Twins Geek, I put together a quick spreadsheet that compares Joe Mauer to a list of the great catchers of the past 60 years plus a few other active catchers. I don't really have any specific point to make, other than it's interesting to see how favorably Mauer stacks up to the all-time greats through each player's age-25 season.

For the comparison, I looked at: Bench, Berra, Carter, Fisk, Russ Martin, McCann, Piazza, Posada, Pudge Rodriguez, Ted Simmons, and Joe Torre. I also threw Jason Kendall in the mix, since he seems to have become the cautionary tale for those concerned about Mauer's future worth.

First, let's look at playing time through the age of 25, as measured by plate appearances: 

Next, I used Baseball Prospectus' Batting Runs Above Replacement to examine the players' total offensive contributions through age 25, adjusted for league, park, era, etc.  The second number is the players' BRAR per 100 PAs, which levels the field for playing time.

I then did the same comparison using WARP3, a rough measure of a player's total contribution to their team (offensive and defensive), again adjusted for era, league, park, etc.

Notice that Mauer actually ranks second in both BRAR and WARP3 when you adjust for playing time through age 25.  He only loses out to Piazza, but it's important to note Piazza only had about half the PAs.

Finally, as a very crude measure of defensive value, I looked at each player's CS%.  These are unadjusted numbers, and are comparing wildly different environments, so take it with a grain of salt.

I think there are some interesting observations to be made from looking at these charts, but I don't know that I need to make them.  It's clear to me that through age-25, Mauer has positioned himself on a hall of fame track.  However, if you look at the catchers who are actually selected to the hall of fame, they each play into their late 30s.  This, obviously, is the biggest obstacle Mauer will face in moving from a great player in his 20s to a hall of famer in his 30s.

Oh, what the heck, I will make one observation.  It seems that the Kendall comparisons may be a bit overstated, when you take into account offensive environments.  League average offense when Kendall was in his early 20s was quite a bit higher than it has been in recent years, which depreciates Kendall's value when we make our adjustments.  When you put the numbers in context, Mauer is considerably better offensively, and threw out a significantly higher number of base runners.