SANTA CLARA, Calif. — San Francisco 49ers All-Pro linebacker Patrick Willis has undergone surgery on his right knee to remove an inflamed fluid sac that kept him out of this year's Pro Bowl.

The 49ers said the surgery, considered minor and done about a week ago, was performed by Dr. Tim McAdams and Dr. Gary Fanton at Stanford Hospitals and Clinics in nearby Redwood City.

Spokesman Bob Lange said there is no infection and no structural damage. The team will not put a timetable on Willis' return, but he isn't expected to be sidelined for long. The team will adjust his offseason conditioning and regimen as he rehabilitates.

Willis played college football at Mississippi.