Washington Redskins head coach Mike Shanahan announced that running back Clinton Portis will miss four-to-six weeks with a groin separation.

"It's a temporary setback. These things happen during the season", Shanahan said.

With Portis out, Ryan Torain will get the starting nod at running back.

A fifth-round pick out of Arizona State by the Shanahan-coached Denver Broncos in 2008, Torain (6-0, 222) is familiar with the offense that Shanahan has brought with him to the nation's capital. Torain saw extensive in place of Portis on Sunday, gaining 70 yards and a touchdown on 18 carries.

Signed off the practice squad in Week 3, Torain has 25 carries for 116 yards on the season.