The injury opened the door for Mike McGlynn, who will get his first career start Sunday, in Jackson's customary place to Herremans' right.
Jackson's tear was part of a brutal opening game whose consequences exposed the NFL's most Darwinian side.
The Week 1 contest also included a horrific season-ending knee injury to fullback Leonard Weaver, concussions to two other Eagles starters, and injuries that ended two Packers' seasons as well.
"I've never seen anything like that," Herremans said.
For every injury, though, there is a backup who sees opportunity. The players understand this, acknowledge that each snap could be career-altering, and accept it.
"You don't block it out, you just have to keep going. That's what we signed up for," said tackle Winston Justice.
"You never want to see any of your teammates get hurt," said wide receiver Jeremy Maclin. "After the game you talk to them . . . just kind of say that you're praying for them and stuff like that. But at the end of the day, people got to step up."
Weaver's absence opened the door this week for fullback Owen Schmitt to land another NFL job. Quarterback Kevin Kolb's concussion will give Michael Vick his first start since 2006.
Reserve linebacker Omar Gaither, expected to start in place of Stewart Bradley, has a job that basically depends on the fact that he will be needed to fill in for others.
"Let's just face it, this is why I made the roster," Gaither said. "You never want to start this way . . . but at the same time, I want to take advantage of the opportunity."
Bradley, he said, would have done the same thing earlier in their careers, when Gaither was the first-teamer.
McGlynn has pointed out that Jackson got his starting job when former center Hank Fraley hurt his shoulder.
"It's just part of the game," McGlynn said.
A career reserve, whose locker sits among the Eagles' backup linemen, McGlynn has waited three years for his chance.
Herremans and Jackson, meanwhile, have adjacent lockers in a stretch that, until recently, belonged exclusively to the five offensive-line starters. (That changed when projected first-team guard Stacy Andrews was traded and replaced with backup Reggie Wells.)
This week, Herremans' green No. 79 practice jersey was in its usual place, draped on a hanger in his stall. In the next locker, Jackson's 67 was absent.
The two gained starting roles within two weeks of one another in 2005, and played together for nearly all of the last four seasons.
Their time together on the field led to a close friendship off it, Herremans said. "We just became good friends and we'll remain good friends no matter what happens."
As the season rolls on, though, Herremans will line up beside a new center.
Downcast after the Packers game, Herremans said "my heart goes out" to Jackson, who he had seen for months rehabbing, lifting weights, and running to get back in time for the opener. But, in his next breath, Herremans looked ahead.
"Football's a game of injuries," he said. "You've got to be able to take it and roll with it."
Contact staff writer Jonathan Tamari at 215-854-5214 or firstname.lastname@example.org.