For the Milwaukee Brewers, what goes around comes around at first base.

Last season, Corey Hart moved from right field to first base after Mat Gamel suffered a season-ending knee injury in early May. Now comes the news that Hart will have knee surgery and miss the first four to six weeks of the season, opening the door for Gamel to return to that position.

The Brewers learned Friday that Hart would need surgery on his right knee to correct a problem that surfaced recently during offseason workouts. He is expected to be out three to four months from the time of the arthroscopic procedure, to be performed Tuesday by team physician William Raasch.

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.

After Hart experienced swelling in the knee, he was examined in Phoenix by Raasch, who ordered an MRI. That test revealed a defect in the joint surface of the knee.

Brewers medical director Roger Caplinger likened the defect to a pothole in a road that must be filled. To do that, Raasch will debride the joint surface to remove damaged tissue, make it bleed and heal in. Raasch also will repair a small meniscus 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.' "

That proved to be the case last spring when Hart recovered from arthroscopic surgery on the same knee during spring training to get ready for the start of the season. In that procedure a significant meniscus tear was repaired, and though Hart suffered occasional soreness he made it through the season and didn't expect further issues.