The Brewers' situation at first base changed Friday when they learned Corey Hart will need knee surgery that will make him miss at least the first six weeks of the 2013 season.

Hart, who had surgery on his right knee last spring to repair cartilage damage, experienced swelling in that same knee during offseason workouts and was examined in Phoenix by team physician William Raasch. An MRI was performed that revealed a defect in the joint surface.

Raasch will perform surgery Tuesday in Milwaukee to repair that defect, knocking Hart out of action for three to four months from the time of the procedure. Hart's rehabilitation will include bearing no weight on the knee for six weeks or so, taking him into early March. At that point, he is expected to need six to eight weeks to get ready to play.

Brewers medical director Roger Caplinger likened the defect to a pothole in a road that must be filled in. To do that, Raasch will debride the joint surface to make it bleed and heal in. Raasch also will repair a small meniscal tear near that defect.

"Corey can't pinpoint it to one specific episode," said Brewers assistant general manager Gord Ash. "He was doing his offseason workouts and the knee started to swell up. So, we're a little stumped on that front. Dr. Raasch did not think it was something that Corey could or should play with. But, like Corey said, 'I'm a quick healer.'"