Sessler: QB race opens in Miami
Garrard later told FOX Sports insider and NFL Network contributor Jay Glazer that he'll have the operation Saturday and doctors believe he'll be out two to four weeks.
"Nothing happened, just Father Time, wear and tear," Garrard told Glazer. "They have to take out loose things floating around."
Garrard's agent, Al Irby, told The Associated Press that the quarterback's knee had been an issue for a few days, and he decided to have surgery.
"He had been feeling some soreness, and he got it looked at," Irby said, according to The AP. "He could have played on it, but they'd rather do the surgery now to make him more comfortable, rather than fool around with it."
Garrard didn't play in 2011 after being released by the Jacksonville Jaguars before the season started. Garrard had back surgery in October.