If he doesn’t hit for more power, Mauer will be an average first baseman

Joe Mauer’s catching days are over.

The Minnesota Twins announced today that Mauer will be moved to first base full time because of his age and the impact of years of catching. Mauer missed the end of last season because of a concussion he sustained while catching.

Mauer, a gifted athlete, will excel at whatever position he plays. But a Gold Glove, batting-title winning catcher is rare — and a lot more valuable than a high-average, low-power first baseman. At $23 million a year, that’s a lot of money to pay.

Mauer led all American League catchers in on-base percentage plus slugging — a statistic that reflects success in hitting and hitting for power — just ahead of Cleveland’s Carlos Santana, who also is spending more time at first base these days.

Mauer, though, would rank only third in the league if he duplicated that stat as a first baseman. And his home run output, even in years when he wasn’t injured, puts him closer to the bottom of starting first basemen in the league.

That could always change with a move to an easier position. Mauer could concentrate more on his gifted hitting, and less on the defense required as a catcher.

How does his future career at first compare to his future as a catcher? It’s actually fairly easy to know.

First, since he’s 30 now, there’s plenty of data to predict using the Brock5 calculations, which predict future performance. The system, developed by the Society of Baseball Research (SABR), also compares each season’s production to others at the same position, because at some point, a player can be replaced by a better player.

Let’s look at Mauer’s future numbers as a catcher:

That’s an everyday player well into his thirties, even though it’s worth noting his batting average is about to tail off sharply. And yet, he remains a full-time player. Why? Because there’s no one coming along to take his job with those numbers, as the Twins will most certainly find out as they try to replace him at catcher.

Now let’s look at the same projection, only moving him to first base.

There’s not much difference over the next few years (the program doesn’t account for Mauer concentrating more on power hitting, only establishing a minimum performance level to keep a job at a particular position), but after that his playing days dwindle quickly.

Why? Because first base is where all great hitters end up (before they become designated hitters) and the numbers Mauer is projected to turn in aren’t good enough to keep him in the lineup in the face of younger, and probably much cheaper players. His career at first is about 200 games shorter than his career as catcher, if, of course, he could physically absorb the damage of catching, which he obviously can’t anymore.

If, on the other hand, he can perform next year with near identical statistics to his 2009 season, check out what it does to his future:

His career lasts another 300 games, and he hits almost 100 more career home runs. That’s what the Twins are hoping will happen in 2014. And that’s why 2014 will be a critical year for determining Mauer’s future with the Twins.

How accurate are these projections? When I last ran one for Mauer in 2010, it predicted that this past season he’d hit .322 with 4 HR 49 RBI and 49 walks in 122 games. He played in 113 games, batted .324 with 11 HR and 46 walks.