FORT MYERS, Fla. -- Damage to Eric Milton's left knee is more extensive than originally thought, leaving the Minnesota Twins uncertain when the left-hander will return to the mound.

	Milton

"I'm not going to try to guess," Twins manager Ron Gardenhire said Thursday afternoon when asked when Milton may be back in the lineup.

Arthroscopic surgery performed on Milton's knee Wednesday revealed loose cartilage rubbing against the top of the knee. The friction made the cartilage flake and the knee swell.

Milton will be on crutches for two weeks before he can begin rehabilitation. Before the surgery, Milton had expressed hope he could return to action after the first week of the regular season.

"I don't know how big of a chunk of the season he'll have left," Twins general manager Terry Ryan said.

The Twins learned about the surgery results during a conference call Thursday afternoon with Dr. Thomas Rosenberg, who performed the operation in Park City, Utah.

"That was one of those conversations where there was a sick feeling in your stomach when you heard the doctor talk," said Gardenhire, who missed the first inning of the Twins-Red Sox game to take part in the phone call.

Milton's agent, Casey Close, said all parties involved want to be patient with Milton's recovery so he can return without fear of future injury.

"The best way to take this is very slowly and conservatively,'' Close told the Star Tribune of Minneapolis on Thursday night, when he said recovery could take three months. "It could be that long. It could be shorter or longer. No one knows a person's recuperative powers.''

Milton was expected to return to Fort Myers on Friday.

The Twins will move left-hander Johan Santana into the starting rotation while Milton is out. It could end up being an extended run if Milton misses several weeks to go through rehabilitation, including a few appearances in minor league games to build his arm strength.