[MLS] The New England Revs' concern over their goalkeeping situation came into clearer focus Thursday when the team announced Matt Reis had undergone knee surgery.

Already sidelined while rehabbing shoulder surgery, a procedure known as quadriceps tendon debridement was performed on his left knee at Massachusetts General Hospital. Rehab time for the knee is from eight to 12 weeks, which combined with his shoulder rehab is expected to keep him out of action for three to four months. Rotator cuff surgery was performed on his left shoulder Dec. 1.

New England lost backup Brad Knighton, who allowed 14 goals in six games last season filling in for Reis, to Philadelphia in the expansion draft. Last month, the Revs acquired goalkeeper Preston Burpo and defender Cory Gibbs from Colorado in exchange for midfielders Jeff Larentowicz and Wells Thompson. Burpo, the backup to Matt Pickens last year for the Rapids, is projected to be the starter in Reis' absence.

Reis, 34, acquired from the Galaxy prior to the 2003 season, posted eight shutouts, led MLS in saves with 114, and compiled his career-best goals-allowed average (0.96) in 2009. He is a four-time MLS All-Star.