ASHBURN, Va. -- Still feeling the effects of a concussion, Redskins running back Clinton Portis was hardly his vivacious, loquacious self when he met with coach Jim Zorn on Wednesday and probably will miss this weekend's game against the Denver Broncos.
"I don't want to rule him out, but it's very doubtful that he's going to play," Zorn said. He then added, in response to a reporter's question: "I would say 'very, very doubtful."
Portis left in the first quarter of Washington's 31-17 loss to the Atlanta Falcons on Sunday after a helmet-to-helmet hit.
"He would play if he could, but he really is sort of mellowed out with this concussion. Just a little quiet. He needs to get rest," Zorn said. "And I think it's a dangerous thing. I would never say, 'Come on, Clinton! You can do it!' That wouldn't be the right thing to try to push, and we're not going to do that. We're going to be cautious."
After their meeting, Portis left the Redskins' practice facility to see a doctor and have some medical tests. He did not speak to reporters.
He ranks eighth in the NFC with 494 yards rushing this season for Washington (2-6), which has lost four games in a row. If Portis does sit out, Ladell Betts -- used mainly as a third-down back -- would get his first start since the last game of the 2006 regular season. Betts, though, missed practice Wednesday with a sprained ankle.
In other Redskins injury news, strong safety Chris Horton had toe surgery Wednesday and was put on injured reserve, ending his season. Horton also was hurt against Atlanta.
Washington filled Horton's roster spot by re-signing running back Quinton Ganther, who was released last week.
"Right now, yeah, that's a 'ruled out' situation for us," Zorn said.
Horton is Washington's third starter to go on IR this season, joining offensive linemen Chris Samuels (neck) and Randy Thomas (triceps). Other regulars expected to miss Sunday's game: Portis, tight end Chris Cooley (ankle), punter Hunter Smith (groin) and tackle Mike Williams (ankle). Zorn said Cooley will sit out for about another two weeks and then will be re-evaluated.
Jason Campbell was limited slightly in practice Wednesday, avoiding too much movement as a precaution because of a swollen ankle, but Zorn said he expects his starting quarterback to be fine for Sunday.
"Just trying to be smart about it," Campbell said. "Don't want to aggravate it."