Since the beginning of training camp, when injuries threatened to rip apart the Eagles' offensive line, one common thread has kept the unit from tearing at the seams.

In a season when four-fifths of the projected line has combined for 32 missed starts, center Jamaal Jackson has been the mainstay.

"I take my hat off to him," left guard Todd Herremans said. "He's been the main cog all year. He's been solid in the middle, keeping everybody together with all the shuffling around. . . . I think he goes underappreciated a lot of times."

Perhaps no longer. Quarterback Donovan McNabb, a four-time Pro Bowl selection, singled out Jackson and Herremans on Wednesday. And there has to be recognition from a line - on display today against the Denver Broncos - that anchors one of the best offenses in the NFL.

"I guess it's a testament to all the work I've been putting in over the seven years," said Jackson, who hasn't missed a game since 2005. "I think it's like 70 straight games. It's got to count for something. It's nice to hear those guys say that. At least I know I have the support of my teammates. That's all I want."

More than likely, that's all the 29-year-old will get. When the Pro Bowl rosters are announced Tuesday, Shaun O'Hara of the New York Giants and Jason Brown of the St. Louis Rams are likely to represent the NFC at center. Nevertheless, another season without recognition is unlikely to deter Jackson, who was undrafted out of Delaware State.

For a number of reasons, his performance this season has stood out amid turnover and turmoil. It all started in the off-season when the Eagles parted ways with their bookends for the previous decade. Tackles Tra Thomas and Jon Runyan weren't re-signed, and Jackson instantly became the veteran of the line.

"Even the last couple of years that they were here, I tried to take it upon myself to establish some kind of leadership role," Jackson said. "But this line is full of leaders. I look at Todd as a leader."

Thomas and Runyan weren't the most vocal but led by example, and that meant being professional and playing through pain. Thomas, now a backup for Jacksonville, missed only eight games because of injury during 11 seasons in Philadelphia. And Runyan, who signed with San Diego a month ago, never missed a game in 10 seasons as an Eagle.

"I kind of learned from Tra and John when they were here," Jackson said. "When I was a rookie, they were the leaders of the O-line, and I just kind of watched them and saw what they did and tried to model myself the same way."

Even before the injuries, there was concern about continuity after the Eagles signed tackle Stacy Andrews as a free agent and traded for tackle Jason Peters in the off-season. The Eagles suggested that Andrews would start. Some figured that he would replace Runyan on the right, and that Peters would step into Thomas' void on the left. But Shawn Andrews, Stacy's younger brother, was moved from right guard to right tackle during minicamp.

'We just roll with it'

If the Eagles had been told during the summer that their right tackle (Shawn Andrews) would be lost for the season, their right guard (Stacy Andrews) would go from being a starter to being inactive on game days, their left guard (Herremans) would miss the first five games, and their left tackle (Peters) would miss one game and parts of three others - and they would still be 10-4 - there might have been cynicism.

"I wouldn't say it's been a disaster," Herremans said. "It's hard to say what you would have said if this was the scenario back then. That's not what we were expecting. The mind-set that we have is, 'Whoever is ready to play has to play, and we just roll with it.' "

So when Shawn Andrews reinjured his back on the first day of training camp and was finished for the season six weeks later, Winston Justice assumed the spot and quickly silenced concerns about his readiness. When Stacy Andrews showed that he was not fully recovered from off-season knee surgery, Nick Cole plugged the hole. When Herremans sat with a stress fracture in his left foot, Cole slid over to left guard and Max Jean-Gilles and Stacy Andrews rotated at right guard. And when Peters suffered through an assortment of aches, Herremans took over on the left flank.

"We battled through some inconsistency, and I'm not talking about the play, I'm talking about the players in and out from injury," offensive coordinator Marty Mornhinweg said.

"We've survived two good players' not playing for us," he said, referring to the Andrews brothers, "and then we had some other linemen that were down for a significant period. I think the players deserve some credit for keeping that together."

The run-blocking has been consistent throughout the season, although, surprisingly, the Eagles have gained less per carry during this five-game winning streak than they did before - 4.1 yards as opposed to 4.5.

The pass-blocking has improved dramatically. In the first nine games, the line allowed an average of 2.4 sacks game. In the last five, the average dropped to 1.6, and McNabb wasn't sacked by San Francisco last week.

The reason for the success?

"Chemistry, man," Jackson said. "Getting Todd and Jason on the same page, getting Winston and Nick on the same page, that kind of solidified everything. I was familiar with those guys because I played with Max last year; I played with Nick last year. It wasn't a hard adjustment for me. It was just the guys playing next to me."

Cohesion and confidence

Herremans said offensive-line coach Juan Castillo's meetings helped foster an environment in which the reserves believe they can play as well as the starters. It's a football cliché about the next guy stepping up, but the Eagles' linemen have done it.

"Everybody knows that the second five can play," Herremans said. "And every time someone gets a chance to step in - and there have been plenty - they want to prove they can play."

Jackson is often responsible for getting the rest of the linemen to meetings on time, and organizes a lot of gatherings that aren't required by the coach. "Pretty much a lot of decisions go through me," he said.

It's that way in games, with Jackson calling out assignments and keeping a cohesive front five from shredding.

"I think sometimes you might take him for granted because he's always been there," tight end Brent Celek said. "And you just expect him to be there."

Contact staff writer Jeff McLane at 215-854-4745 or jmclane@phillynews.com.