Orton came up hobbling after being tackled on a third-down scramble right before halftime. He was on the sideline during the second half, his ankle heavily taped.
"I was hoping to come back out, and I just wasn't able to," said Orton, who completed 11 of 18 passes for 193 yards and two long touchdowns to Brandon Marshall.
Coming out of halftime, Orton said he tried a few practice throws but then told coach Josh McDaniel he wouldn't be able to play.
Orton said after the game that it was too soon to say whether he would be able to start against the San Diego Chargers next Sunday.
"I'm not going to sit here and talk about it," he said.
Backup Chris Simms played the second half against the Redskins for his first action this season. And the rust showed: Simms completed 3 of 13 passes for 13 yards and an interception, which translates to a passer rating of 7.5.
For comparison's sake, Orton's passer rating in the game was 134.7.
"We'll see what happens with Kyle," Simms said. "If I get a full week of reps in practice under my belt, I'll be able to go next Sunday."
Copyright 2009 by The Associated Press