Ashburn, VA -- (Sports Network) - The injury-ravaged Redskins will be without running back Clinton Portis when Washington takes the field Sunday against the Broncos.

Portis suffered a concussion early on in Washington's 31-17 setback to Atlanta last Sunday and did not return. The veteran back has been beset by injury this season and last, yet had suited up for each of the 'Skins eight games thus far in 2009. He has 494 yards on the ground and 57 through the air with a combined two scores this season.

Meanwhile, Portis' backup, Ladell Betts, remains sidelined with an ankle injury and sat out practice for a second straight day Thursday. Betts rushed for 70 yards and a score on 15 carries last week after taking over in the backfield.

Quarterback Jason Campbell was able to take full reps on Thursday after being limited due to an ankle injury on Wednesday. Punter Hunter Smith remains a question mark due to a right groin ailment. He was limited on Wednesday and did not participate Thursday.

The offensive line continues its shuffling of personnel with starting tackle Mike Williams out with an ankle injury. Fellow tackle Stephon Heyer was limited Thursday with a knee injury for an already thin unit minus two starters for the season in Chris Samuels and Randy Thomas.