"I really don't know for sure," Shanahan said Sunday. "That's why it's day by day. We'll see how it goes."
Shanahan said the leg is too sore for McNabb to play this week against the Arizona Cardinals, but McNabb likely wouldn't have played in that game anyway because the coach prefers to rest his starter in the final exhibition to avoid injury.
That leaves bubble quarterbacks John Beck and Richard Bartel taking the snaps Thursday at Arizona.
The news from Shanahan was more positive concerning running back Clinton Portis, who sprained his right ankle against the Jets.
"I don't think it's too serious. It's not a big setback," Shanahan said. "I would anticipate him being able to practice in a couple of days."
Copyright 2010 by The Associated Press