"It's still sore," Redskins coach Mike Shanahan said on the team website (www.redskins.com).
"I don't think he could go if it were a regular season game, so he has to rehab it and get it better," Shanahan added.
McNabb injured the ankle in last week's preseason game against the Baltimore Ravens. He watched practice from the sidelines on Tuesday with the ankle wrapped.
Rex Grossman is expected to start at quarterback for the Redskins.
(Reporting by Gene Cherry in Raleigh, North Carolina; editing by Rex Gowar)