Defensive tackle Brandon Noble underwent arthroscopic surgery on his left knee on Wednesday and could be sidelined 4-6 weeks, team officials said.
Noble had tweaked the surgically repaired knee during a practice last week, forcing him to sit out the Sept. 11 season opener against the Chicago Bears.
"You hate that he gets a setback on something like that," head coach Joe Gibbs said. "Our first thought is to always protect him and do what is best for him."
In 2003, Noble had reconstructive surgery on his left knee after suffering an injury during a preseason game. The 6-2, 305-pounder returned last year to play in all 16 games, with seven starts.
Noble recorded 38 tackles (19 solo) and one sack in 2004 and was named the team's Ed Block Courage Award winner.
Added Gibbs: "[Winning the Ed Block Courage Award] says a lot about his work ethic and how mentally and physically tough Brandon is."
Coming out of preseason, the Redskins had decided to keep five defensive tackles. Noble is listed as a backup to starters Cornelius Griffin and Joe Salave'a. In Noble's absence, Ryan Boschetti and Cedric Killings could see increased action in the defensive line rotation.