Hey, Joe Mauer is having a good season

It's gone completely under the radar since the Twins have been terrible, thanks to a historically awful starting rotation, but Joe Mauer is hitting .312/.407/.431, putting his injury-plagued 2011 behind him. While that's still a far cry from his 2009 MVP numbers -- .365, 28 home runs -- it's obviously terrific production from a catcher. Of course, Mauer has only started 58 games behind the plate, as the Twins have attempted to keep him healthy, so his value doesn't come close to what it would be if he was catching on a regular basis.

That .407 on-base percentage leads the American League (tied through three decimal points with Prince Fielder), which seems like a low league-leading figure. Indeed, the last player to lead the AL with a lower OBP was Dwight Evans of the Red Sox with a .402 figure in 1982. The last NL leader with a figure less than .407 was Kal Daniels of the Reds with a .397 mark in 1988. If you're too young to remember Daniels, he was a terrific hitter with power and patience. He was just 24 in 1988, but knee injuries ruined a promising career and that was the only season he ever played 140 games.

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Speaking of catchers who can hit, Kansas City's Salvador Perez is hitting .295/.319/.494, excellent numbers for a 22-year-old backstop. Perez's season got off to a late start due to a torn meniscus suffered in spring training, but he's been smoking line drives since returning in late June. While he has just 185 plate appearances, the numbers are still pretty rare for such a young catcher. Since 1950, only six 22-year-old catchers with at least 200 PAs have compiled an .800 OPS:

Brian McCann, Braves, 2006: .961

Ivan Rodriguez, Rangers, 1994: .848

Ted Simmons, Cardinals, 1972: .801

Earl Williams, Braves, 1971: .815

Johnny Bench, Reds, 1970: .932

Bill Freehan, Tigers, 1964: .812

Those guys all had at least 400 PAs and I'm certainly not comparing Perez to Bench, who won the MVP Award that season. The first three guys are interesting comparisons, however:

McCann: 8.3% BB rate, 11.0% SO rate, 4.9% HR rate

Rodriguez: 7.7% BB rate, 10.4% SO rate, 4.0% HR rate

Simmons: 4.6% BB rate, 9.1% SO rate, 2.5% HR rate

Perez: 3.2% BB rate, 7.6% SO rate, 4.3% HR rate

Like those three, Perez is an excellent contact hitter. Among those with at least 170 PAs this season, Perez owns the sixth-lowest strikeout rate. Of course, he also owns the sixth-lowest walk rate. While he does expand the strike zone a bit (he's 27th in percentage of swings on pitches outside the strike zone), he's not a completely wild hacker. His low walk rate is also derived from his high contact rate -- only Marco Scutaro and Juan Pierre swing and miss less often.

Perez is a completely different hitter than Mauer, a guy who waits for his pitch and takes his walks. But I could see Perez developing into a Ted Simmons-caliber hitter. Simmons' walk rate jumped as a 23-year-old and he turned into one of the better hitting catchers of all time, a guy who hit .300 seven times and reached 20 home runs six times. If Perez can learn to be a little less aggressive at the plate, he has Simmons-like potential. That's high praise; but as we learned with Mauer and Perez already, injuries are always a huge factor in a young catcher's potential development.