IRVING, Texas - Jason Garrett stubbornly refuses to acknowledge that the Dallas Cowboys are likely to play the most important game of their season without quarterback Tony Romo.

Owner Jerry Jones isn't ready to concede that point, either.

Garrett insists on saying the Cowboys will evaluate Romo on a day-to-day basis despite reports that the quarterback has a herniated disk that could require surgery. The coach wants his team to focus on Sunday night's regular-season finale against the Eagles, a game that will determine whether the team ends a three-year playoff drought.

"All I'm saying is he has back spasms, symptoms that we're treating as we go along in the week to see if he will play," Jones said. "There is nothing structurally that will rule him out if he feels good and is cleared to play. Nothing."

Kyle Orton is the only other quarterback on the roster and is likely to start in Romo's place. Garrett's admission that the Cowboys will look to sign another quarterback - three are lined up to work out at Valley Ranch on Tuesday - is a clear signal that Romo's availability is in serious doubt.

Club officials were largely mum regarding Romo once the results of his MRI exam were known. Late Monday evening, a source said "it was too early to comment" on whether the quarterback has a herniated disk, a response that suggests a second opinion is being sought.

"It's the next-man-up philosophy," Garrett said of the possibility that Orton will start his first game in nearly two years. "That's alive and well in our organization. . . .

"Kyle has played in this league for a long time. He has started a lot of games. Guys have a lot of confidence in him. . . . We feel awfully good about that situation if Tony is not available."

For the third consecutive season, the Cowboys can make the playoffs if they win their final regular-season game. They lost the last two seasons with a healthy Romo.

The team's chances of clearing that hurdle without him are diminished. Orton has a 35-34 record as a starter in 10 NFL seasons. He has never started a regular-season game for the Cowboys.

"Obviously, Tony is a big part of everything we try to do as a football team and an offense," tight end Jason Witten said. "He's been pretty resilient, and I know he'll do everything he can to get back."

Drew Dossett, an orthopedic surgeon, removed a cyst from Romo's back in April that kept him from taking part in practice during the team's offseason program.

Romo aggravated his back when twisting to avoid a rush and throwing a completion to Miles Austin early in the fourth quarter of Sunday's comeback victory over Washington. He did not come out of the game.

Romo is 63-45 as the team's starting quarterback since taking over in Week 8 of the 2006 season. The team is 6-7 in games he has missed because of injury.

Garrett was asked how he would deal with the emotional haymaker of losing Romo before the team's game with the Eagles.

"We've dealt with injuries all year long, just like everyone has," Garrett said. "We literally have dozens and dozens of examples on our football team of younger guys stepping in and playing.

"The emotional part is, you're a pro. You've got to be ready to go do it. The guys around you have to continue to do their job, and you go forward."

Garrett concedes that logistically the club will sign another quarterback because you can't go through practice with just one. David Carr, Tyler Thigpen, and John Skelton are scheduled to work out at Valley Ranch on Tuesday.

Adding to the uncertainty of Romo's status is a comment by the quarterback's father. When contacted Monday evening, Ramiro Romo said he's not sure how badly his son is hurt but is considering flying to Dallas to see him.

Garrett made it clear the Cowboys haven't ruled Romo out. But for now, they must proceed as if he won't play Sunday.

"I hope not, obviously," Witten said. "But we'll just wait and see."