Linebacker LaVar Arrington underwent arthroscopic surgery on Thursday to repair a lateral meniscus tear in his right knee, a procedure that will force him to sit out Monday night's game against the Dallas Cowboys, team officials said.
His status for future games will be evaluated on a week to week basis.
Accompanied by the team's director of sports medicine, Bubba Tyer, Arrington traveled to Birmingham, Ala., Thursday to have his knee examined by Dr. James Andrews, the team's senior medical consultant.
A decision on the surgery was made Thursday afternoon. Arrington and Tyer were expected to return to the Washington, D.C., on Thursday evening.
Arrington sprained his knee during the season-opening win against Tampa Bay but was able to finish out that game and start last Sunday's Week 2 game against the New York Giants.
The Redskins have several options in replacing Arrington at the weak-side linebacker position.
Backup linebacker Lemar Marshall would be one possibility. Marshall is a third-year player out of Michigan State who has played mostly on the Redskins' special teams the last two years.
If Mike Barrow is able to return from knee tendinitis that has sidelined him the first two games, then another possibility would be to start him at middle linebacker and Antonio Pierce at weak-side. Pierce has played all three linebacker positions in the pros and he started the first two games at middle linebacker for Barrow.
"There's a chance of that happening, but it depends on what Mike Barrow feels like," Gibbs said.
Linebacker Marcus Washington compared Marshall's opportunity to that of Pierce's opportunity to start for Barrow.
"He's another guy who'll be excited to get an opportunity to play well," Washington said.
Arrington had initially been listed as questionable for this Monday's game. His knee had taken a turn for the better on Wednesday, but Gibbs said some swelling occurred overnight into Thursday.
"We are going to have to go until LaVar gets back," Gibbs said. "He played last week with it and we thought he did a great job for us. It's just one of those things that happens and you need to get it taken care of. LaVar is somebody we think is going to play for a long time. So we want to make sure we take good care of it."
Arrington has recorded 15 tackles (eight solo) so far this season. In the Week 1 victory over the Tampa Bay Buccaneers, his sack of quarterback Brad Johnson on the last play of the game sealed the win.