ASHBURN, Va. - Donovan McNabb to second-string. Then to third-string. Then no guarantee that he'll be back next season.

The ever-dramatic Washington Redskins upset the NFL apple cart once again yesterday when coach Mike Shanahan announced Rex Grossman as his starter for the rest of the season, beginning with tomorrow's game at Dallas.

McNabb will be the No. 2 quarterback against the Cowboys, then drop to No. 3 behind Grossman and John Beck for the final two games of the season.

"I also told him," Shanahan said, "that I cannot guarantee him that he will be back next year."

That's how far the 34-year-old, six-time Pro Bowl quarterback has fallen. The player acquired with such fanfare from the Eagles in an April trade is benched in a season in which he has been woefully inconsistent, throwing a career-high 15 interceptions and ranking 25th in the NFL with a 77.1 passer rating.

Asked if getting McNabb was a mistake, Shanahan said: "I think there's a lot of mistakes that you make. You really don't know if you made a mistake, but if you do make one, you make it and you go on. What I want to do is evaluate where we're at the end of the season, then I will tell you if we erred or not."

Shanahan said he had been planning to make the move after the Redskins (5-8) were mathematically eliminated from the playoffs, which happened last weekend after a 17-16 loss to Tampa Bay.

"I've got to find where Rex Grossman is, where John Beck is. I want a chance to evaluate these guys," Shanahan said. "I told Donovan that there's nothing he could do in the three games that would influence me over what he's done over the last 13 games."

McNabb did not comment yesterday, saying "No! No! No!" to reporters as he entered Redskins Park after practice. McNabb's wife abruptly canceled a scheduled interview with the Associated Press in which she planned to promote a charity event involving NFL wives.