Practice will be more vital than ever for the Eagles this week as they prepare for their showdown against the Dallas Cowboys with the NFC East title and a few other things on the line.

That's because the man who had started every offensive play this season for the Eagles before Sunday is finished for the season.

Eagles coach Andy Reid broke the bad news at the top of his news conference yesterday when he announced that center Jamaal Jackson suffered a torn anterior cruciate ligament in his left knee during the first quarter of the Eagles' win against the Denver Broncos.

During the game, Nick Cole moved from right guard to center to replace Jackson, and was replaced at right guard by Max Jean-Gilles. The Eagles, who have a six-game winning streak, will likely continue with that setup against the Cowboys, but it will be difficult to match the high level at which Jackson, Cole, and left guard Todd Herremans had been playing.

"We're happy we got out of there with a win, and we can move on to this week and get into practice, which is going to be a huge thing for us," Herremans said.

Neither Herremans nor tackle Winston Justice tried to sugarcoat the loss of Jackson, who had started 71 straight games.

"It's a big loss," Justice said. "Jamaal had stepped up as the leader of our offensive line, and when you have someone that pivotal on the line go down, it's a big hit."

Herremans spoke to his close friend Jackson yesterday morning after he underwent an MRI examination.

"He was real down," Herremans said. "He said, 'Go ahead and make sure I get a ring.' He said, 'You have to lead these guys now. You're the veteran out of all those guys.' It's terrible. I feel awful for Jamaal just because he has worked so hard, and he has been so constant and such an integral part of our offense."

The offense had problems after Cole replaced Jackson. In addition to a fumbled exchange between Cole and quarterback Donovan McNabb at the Eagles' 1-yard line and a shotgun snap that hit running back LeSean McCoy, there were three false-start penalties - one each on Jason Peters, Justice, and Herremans.

"There were a few penalties, and stuff like that can kill your momentum," Herremans said. "I'm not saying they were on Nick. . . but the chemistry and the flow you have with each other and the timing you had with Jamaal is going to be different from Nick. Certain things do change and penalties definitely kill the momentum of the game, and some of it probably did have to do with Jamaal going down."

Cole has a particularly difficult assignment against the Cowboys. He'll be matched against 6-foot-4, 304-pound Jay Ratliff, whose six sacks are the most among NFL nose tackles.

As always, Reid's mentality was that the next guy in line has to do the job.

"It's obviously a big loss," the coach said, referring to Jackson. "He's a good football player. We're fortunate enough to have Nick here, who's a center who has been playing guard for us. This isn't a new territory for him. It's one that he's had a chance to play before, and he and Donovan are on the same page."

Cole played tackle and guard at New Mexico State, but became the Eagles' backup center as an undrafted rookie in 2006. He has remained in that role the last three seasons, but has also started all 15 games this season, five at left guard and 10 at right guard.

His teammates have confidence in him.

"Nick has played center before, and he has always known in the back of his mind that if anything happened like this, that's where he'd have to go," Herremans said. "I think he's ready to take on the responsibility."

Jean-Gilles has experience as a starter at right guard. He replaced Stacy Andrews as the starter for four games earlier this season while Cole filled in for an injured Herremans at left guard. Jean-Gilles also started 10 games at right guard last season.

"We have had to go through [the offensive-line injuries] all year," Herremans said. "The biggest thing is that when somebody has gone down, people have stepped up and played well. You're not always guaranteed who is going to play every week, so the five that are able to go have to be ready, and then we roll with it."

Eagles at Cowboys Sunday at 4:15 p.m. (Fox29) Line: Cowboys by 3

Inside

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Tony Romo's recent play makes the Cowboys dangerous. C2.

The Colts' benching decision could affect morale. Ashley Fox, C2.

Contact staff writer Bob Brookover at 215-854-2577 or bbrookover@phillynews.com.