IRVING – As the Cowboys complete their final preparations for Sunday's game against Seattle, they might have to do without Pro Bowl nose tackle Jay Ratliff.

Ratliff did not practice Friday after spraining his knee in Thursday's practice at Cowboys Stadium. He is listed as questionable.

If Ratliff cannot play, Junior Siavii will make the first start of his career and Marcus Spears will serve as the backup. Jason Hatcher would take over Ratliff's role in the nickel and dime defenses.

"We think it will get well, but how quickly it will get well we don't know for sure," coach Wade Phillips said.

Ratliff leads the Cowboys' defensive line with 31 tackles. He also has two sacks, five tackles for losses and 10 quarterback pressures. He has also blocked a field goal attempt.

"He's a Pro Bowl-caliber player and he's playing at that level this year again," Phillips said. "He's not out yet, but if he weren't to play that certainly sets you back some."

It would be the first game Ratliff has missed since the 2007 season finale vs. Washington, when he was rested because of a knee injury. Siavii has 15 tackles and two quarterback pressures in a reserve role this year.

Roving practices this week: The Cowboys practiced at three locales this week: Valley Ranch, Cowboys Stadium and, on Friday, Southlake Carroll.

With the heavy rains, the new Cowboys practice fields have not drained well and have not been usable.

"You feel like a nomad," wide receiver Patrick Crayton said. "You don't know where home is right now. It's like we're the friend sleeping on the couch right now and we just bounce to everybody's stadium."

The Cowboys have also practiced at Coppell High School and Carrollton's Standridge Stadium.

Ogletree may be activated: With Allen Rossum out of Sunday's game, the Cowboys could make rookie wide receiver Kevin Ogletree active.

Ogletree has dressed for one game, averaging 23.5 yards on four kick returns vs. Kansas City, and is a favorite of owner and general manager Jerry Jones.

"It's always good to be recognized by your boss and doing the good things," Ogletree said.

Briefly: Jones said the roof and doors of Cowboys Stadium will be open Sunday provided the forecast holds true: high of 70 with no rain. The roof and doors were open for the home opener vs. the Giants. They were closed last week vs. Atlanta.

As expected, cornerback Allen Rossum is out with a hamstring injury. Running back Marion Barber (thumb), safety Gerald Sensabaugh (thumb) and linebacker DeMarcus Ware (foot) are probable. ... Marcus Trufant, Seattle's 2007 Pro Bowl cornerback, was activated and is expected to make his season debut Sunday. He's been out with back trouble.

With a noon kickoff, parking lots at Cowboys Stadium open at 8 a.m. The plazas open at 9 and the stadium gates open at 10.

The Associated Press contributed to this report.