The Greatness Of Joe Mauer

On the front page, over there on the right hand side, you’ll see some top five leaderboards for our win based statistics that we track on the site – WAR and WPA. If you look at the top of the list for batters in WAR, you’ll notice Joe Mauer has ascended to the pinnacle, as his 3.8 wins above replacement to date leads all major league position players.

Now, to rack up a +3.8 win value through mid-June is impressive enough on its own. Our fair value salary estimate suggests that Mauer has already played well enough to justify a $17 million contract for 2009, and we’re still a few weeks away from the all-star game. Even more amazing, of course, is that Mauer missed the first few month of the season with a back injury that landed him on the DL. Mauer has racked up his 3.8 WAR in just 43 games, totaling 190 plate appearances.

If we prorated Mauer’s performance out over a full catcher season, plus giving him some time at DH, we’d be looking at a +12 WAR season. The only guy to put up 12+ WAR in a single season since ’02 (as far as our numbers go back) is Barry Bonds, and we’ll just say that there’s a wee bit of controversy surrounding that guy.

So, there’s no doubt, Mauer’s having an incredible season. Playing a +12 win level, even for just a few months, is pretty remarkable. But, here’s the thing – our version of WAR probably underrates Mauer, because we don’t try to quantify the defensive value of each catcher. Because of the problems in evaluating catcher defense, for right now, we just assume they’re all average for the purposes of calculating win values. Of course, they aren’t all average – some are demonstrably better than others.

Mauer is one of those better than average guys. Baseball-Reference tracks “runners bases advanced” and “runner kills”, which quantifies how many bases opposing runners are able to take with a certain catcher behind the dish (whether via SB, PB, or WP) and how many times a catcher is able to gun down a runner on the bases. Mauer’s allowed 27 baserunner advancements and has seven runner kills, for a 3.91 rate of advances-to-kills. The league average is 4.96. This isn’t new, either – his career rate is 3.47.

We don’t have a good way of evaluating the other stuff catchers do, or how their responsibilities behind the plate translate into the batter/pitcher match-up. But, there’s certainly not any evidence that Mauer is below average at that stuff, either – the Twins have their highest BB/K rate and lowest opposing BA, OBP, and SLG when he’s behind the plate of any of their three catchers. Despite having a rotation full of guys with fairly pedestrian stuff, the Twins pitchers keep outperforming expectations, and some of that credit has to go Mauer’s way.

If we knew how to evaluate catcher defense well, odds are pretty good we’d be adjusting Mauer’s win value up even higher than it is now, likely pushing him over the +4 win plateau. He’s played 43 games, and he’s already had a full, all-star worthy season.

Right now, Joe Mauer is the most valuable player in the American League, and it isn’t particularly close.