"Washington Redskins running back Clinton Portis will miss four to six weeks with a third-degree separation of his left groin, Coach Mike Shanahan said Wednesday, leaving the bulk of the team's carries - at least temporarily - for second-year back Ryan Torain, who has a history of injuries himself.

Portis suffered the injury in the third quarter of Sunday's 17-12 victory at Philadelphia, a game in which he rushed for 55 yards and Torain added 70, including a touchdown. Shanahan said Portis's injury would not require surgery.

"It's a temporary setback," Shanahan said. "Those things happen during the season. Clinton's tough. He'll get a lot of rehab here. Hopefully, it'll be four weeks rather than six weeks, but a third-degree separation is off the bone.

"So it's quite sore right now. He was tough enough to go back in, give us everything he had, played extremely well during the game, so that's disappointing that working hard and playing so well that he had that setback."

Portis, 29, had 195 yards and two touchdowns on 49 carries in four games this season, and also caught four passes for 41 yards. He played only eight games in 2009 after suffering a concussion in a November game at Atlanta. He needs only 681 yards to break John Riggins's all-time Redskins record for most rushing yards, but is in the last year of his contract.

The Redskins have only two other running backs - Torain and Chad Simpson - on the active roster. Keiland Williams, an undrafted free agent out of LSU, made the team out of training camp but has since been relegated to the practice squad. He could be elevated for Sunday's game against Green Bay."