'Skins RB Portis doesn't practice, listed as questionable

ASHBURN, Va. -- Washington Redskins running back Clinton Portis did not practice again Friday and will be used only "in a limited fashion" if he is able to play Sunday night against the Dallas Cowboys.

The NFL's second-leading rusher was able to watch practice -- unlike Wednesday and Thursday, when his sprained left knee kept him away from the field -- and was "getting some mental reps in case he has a chance to go," according to coach Jim Zorn.

Portis sprained the knee in the 23-6 loss to the Pittsburgh Steelers before last week's bye. He is questionable on the injury report.

"I would use him, if he could go, in a limited fashion," Zorn said.

Portis' backup, Ladell Betts, is probable after missing three games with a sprained knee. Betts was limited in practice Friday.

"We're just trying to get his knee ready," Zorn said. "It was sore a little bit today because of the work he put in yesterday."

If neither Portis nor Betts can play, midseason signing and former league MVP Shaun Alexander would make his first Redskins start.

Cornerback Shawn Springs (calf) and Marcus Washington (shoulder) both practiced for the first time this week. Washington is probable and Springs is questionable, although Zorn said he was "more encouraged" about Springs' chances of playing than about Washington's chances.