March 22, 2009
Mike Redmond will take over as the starter behind the plate, with either Jose Morales or Drew Butera (or perhaps both) serving as his backup. Redmond has hit .327/.382/.426 against left-handers over his career, including .350/.398/.439 from 2006-2008, so being without Mauer versus southpaws won't be a major downgrade for the Twins' lineup. Mauer posted flukishly big numbers versus lefties last year, but from 2006-2008 hit .329/.393/.432 against southpaws to nearly duplicate Redmond's career mark.
However, replacing Mauer against right-handers is a much different story. Mauer has hit .326/.417/.493 against righties over his career, including .324/.419/.481 during the past three years. Redmond has hit .273/.329/.332 against righties over his career, including .280/.313/.322 during the past three seasons. The gap from Mauer to Redmond versus righties figures to be about 100 points of on-base percentage and 160 points of slugging percentage, which would obviously cost the Twins a ton of runs.
To put those numbers into some context, consider that Justin Morneau is a career .281/.348/.498 hitter overall. Take away 100 points of on-base percentage and 160 points of slugging percentage, and you get a near-perfect fit for Juan Castro's career .228/.268/.331 line. Morales is a switch-hitter and batted .318/.373/.421 in 475 plate appearances against righties during two seasons at Triple-A, so whatever playing time he gets in place of Redmond should definitely come with a right-hander on the mound.
As for Butera, he's a right-handed batter with a Castro-like .215/.287/.324 line over 528 trips to the plate at Double-A and zero experience at Triple-A, so he figures to be pretty awful regardless of which hand the opposing pitcher is throwing with and realistically should be viewed as little more than a defensive replacement. Being without Mauer will cost the Twins a significant number of runs, but determining an exact number is difficult without knowing specifically how Ron Gardenhire plans to replace him.
For instance, if Redmond starts against all lefties and splits starts verus righties with Morales, the duo is capable of matching and perhaps even slightly bettering the .257/.325/.390 line that MLB catchers as a whole produced last year. In that case, the dropoff from Mauer should be around one run each week. That may not sound like much, but one run per week represents a difference of 35-40 runs per season and each 10-run change is typically worth about one win. One run per week adds up in a hurry.
In other words, even if the Redmond-Morales platoon is utilized properly and both players perform well in their roles, being without Mauer would likely cost the Twins approximately one win every two months and 3-4 wins over the course of an entire season. Utilizing a Redmond-Morales platoon improperly by playing Redmond against most righties would increase the number of runs lost and pairing Redmond with Butera instead of Morales would magnify the dropoff even further.
All of which is a long way of saying that being without Mauer for a few weeks would cost runs, but being without Mauer for a few months would cost wins. Redmond is among baseball's best backup catchers and Morales has hit well enough at Triple-A to suggest that he's a capable backup too, so the Twins are as well-equipped to weather the loss of an MVP-caliber backstop as could be expected. Still, Mauer is so much better than the average catcher that well-equipped or not his absence is a huge blow.