It could be a smoke screen or just a cautious assessment of his quarterback's health, but Mike Shanahan says he's not certain Donovan McNabb will be available for the Washington Redskins' season-opener against the Dallas Cowboys.

"I really don't know for sure," Shanahan said Sunday. "That's why it's day by day. We'll see how it goes."

McNabb hasn't practiced since spraining his left ankle in the second preseason game against Baltimore. He sat out Friday's game against the New York Jets and watched Sunday's practice with a black sleeve on his left leg.

Shanahan said the leg is too sore for McNabb to play Thursday against the Arizona Cardinals, but McNabb likely wouldn't have played in that game anyway because the coach prefers to rest his starters and some of his top backups in the final exhibition to avoid injuries. No. 2 quarterback Rex Grossman said he won't play this week either, leaving John Beck and Richard Bartel to take the snaps against the Cardinals.

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."

Fullback Mike Sellers, who missed the Jets game, remains day-to-day with a sprained left knee.

Bengals release WR Bryant: The Cincinnati Bengals have released wide receiver Antonio Bryant, who got a four-year, $28 million deal in March but has been sidelined by a bad knee during training camp.

Jets release WR Coles: The Jets have released Laveranues Coles, a move that likely signals the end of the popular wide receiver's career.

The 32-year-old Coles, signed to his third tour with the Jets last month, had four catches for 19 yards in three preseason games.

Sunday's result

Broncos 34, Steelers 17: Dennis Dixon got his first significant playing time with the starters, after Ben Roethlisberger was pulled midway through the first quarter, and didn't make a good impression, throwing two costly interceptions in Pittsburgh's loss to host Denver.

Dixon finished 9-of-16 for 94 yards, two interceptions and a pair of sacks by Robert Ayers.

Quarterback Tim Tebow made his home debut for Denver. After throwing an interception in the second half, he quickly atoned, driving Denver 74 yards in five plays, capped by a 3-yard touchdown strike to fellow rookie Eric Decker.