A short time ago Brewer Media Relations Director Mike Vassallo tweeted the following:
Dr. William Raasch performed surgery today on 1B Corey Hart. He debrided the right knee joint surface and repaired a small meniscal tear.— Mike Vassallo (@MikeVassallo13) January 25, 2013
He later added that Hart's recovery time is expected to be four months.
Earlier reports indicated that Hart was expected to be out 3-4 months, so now we're looking at the long end of that timeframe. Joe Block did the math and noted that missing four months would put Hart back in action on May 25 for the Brewers' 48th game of the season. It's worth noting that Hart was also back in action before he was expected to be ready last spring.
The Brewers have publicly stated that they're comfortable with Mat Gamel starting at first base in place of Hart until their incumbent first baseman is ready to return, but that was before they knew it's probably going to be most of April and May. Gamel is a career .229/.305/.367 hitter in 106 major league games, including a .246/.293/.348 line in 21 games before tearing his ACL last season.