Forrest Griffin has knee surgery

LAS VEGAS -- Former UFC light heavyweight champion Forrest Griffin underwent successful knee surgery on Tuesday to repair damage to his ACL and MCL.

Griffin, 33, suffered the injuries while training for a planned bout against Phil Davis at UFC 155 on Dec. 29. Davis was eventually pulled from the card.

No timetable has been given on Griffin's return, although his head coach Jimmy Gifford said the recovery process would be "lengthy."

"Right now, he's going to concentrate on getting healthy and spending time with his family," Gifford told ESPN.com. "He's taking it one day at a time;, he's in no rush. There's nothing on the horizon."

Griffin (19-7) had originally been scheduled to fight Chael Sonnen in the UFC's year-end card, but that fight fell through when Sonnen accepted a coaching job opposite Jon Jones on an upcoming season of "The Ultimate Fighter" reality series.

That left a spot for the 28-year-old Davis (10-1), who is considered one of the top prospects in the sport. Gifford said Griffin was in peak form when the injury forced him to withdraw.

"He was really excited to fight Phil," Gifford said. "He's an up-and-coming guy, he's not a veteran like Tito (Ortiz) or Rich (Franklin). He was pretty confident he could beat Phil. He looked great in camp, it was a real tough break."