Associated Press It could be a smoke screen or just a cautious assessment of his quarterback's health, but Mike Shanahan says he's not certain that 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.