Brandon Brooks left in the first quarter of the Eagles’ 17-9 loss to the Seahawks with what the team described as an “illness,” but team sources told The Inquirer the anxiety that had previously afflicted the Pro Bowl right guard returned and forced him from the lineup.

Eagles coach Doug Pederson, asked if Brooks’ early departure had anything to do with anxiety, said Sunday that he had yet to talk to the team’s medical staff.

“He just got sick and just had an illness,” Pederson said, “and we had to make a sudden change.”

Brooks wasn’t in the locker room after the game. He didn’t respond to a message seeking comment.

In 2016, Brooks missed two games when, just before warm-ups, he suffered panic attacks. He had endured similar bouts during his tenure with his Texans. He has spoken openly about his struggles and has said that a fixation with perfection has often led to debilitating pregame nervousness.

But Brooks had seemingly overcome his anxiety, and over the last three seasons would become arguably one of the best guards in the NFL. Two weeks ago, the 30-year old signed a four-year, $56.2 million extension with the Eagles that, at the time, had made him the highest-paid guard in the league.

» FROM NOV. 12: For peerless Eagles guard Brandon Brooks, anxiety and injury are no match

With some players, a new contract can relieve pressures. But for others it can lead to stress from wanting to fulfill such a commitment. Brooks didn’t have his best game in last week’s loss to the Patriots, but he wasn’t the only one on the Eagles’ offense, especially after right tackle Lane Johnson left with a concussion.

Johnson was again sidelined for Sunday’s game, which meant that Brooks would need to perform at a high level with rookie Andre Dillard to his right. Dillard had never previously played right tackle at any level.

It showed. Dillard performed so poorly that he was benched at the half. If Johnson’s absence had affected Brooks, to the point where he had to leave, it might prove to be one of the more devastating non-quarterback injuries in team history.

Halapoulivaati Vaitai initially replaced Brooks on the Eagles’ third series, and when Dillard was hooked, Vaitai slid to right tackle. Matt Pryor took Vaitai’s spot at right guard for his first extensive NFL action. Needless to say, the offensive line was a sieve for most of the day as quarterback Carson Wentz often had little time to throw.

“It’s tough. It’s got to be the next man up,” left tackle Jason Peters said. “That’s why you got to work and prepare yourself like you’re a starter for moments like this. You got Vaitai and Pryor — they tried to step in — but, man, it’s tough when you’re sitting back not thinking you’re going to play during the week.

“You’re not ready, stuff like this is going to happen. It’s a learning experience for them.”

If Johnson has to sit another week, Peters said that he would consider moving to right tackle. He said the possibility was discussed last week, “but we didn’t pull the trigger.” The Hall of Fame-caliber tackle hasn’t played on the right side since early in his 16-year career.

“It wouldn’t be super foreign, but it’s a possibility with Lane being out,” Peters said. “I might have to just do it for the team.”

Johnson was in the protocol as of Friday, and wasn’t permitted to be at the stadium, per NFL rules for concussions, but expectations are that he will be cleared by Sunday’s game at the Dolphins.

While Dillard had performed well in place of Peters during a three-game stretch, last week he compared moving from left to right tackle to learning how to write with your opposite hand. While that may have seemed like hyperbole, he said it ended up playing out that way.

“If you do something one way your whole life and then you suddenly got to change it for the next five days, how would you feel?” Dillard said. “It’s tough. I just do my best for the team.”

Even with All Pro defensive end Jadeveon Clowney out with a hip injury, Dillard couldn’t contain the assortment of other edge rushers Seattle sent his way.

He said that he would learn from his mistakes, and when asked how he survived a similar setback as a freshman at Washington State, Dillard pointed out that he would become “one of the best left tackles to go through that school.”

Left guard Isaac Seumalo knows what it’s like to be benched. He lost his starting spot after a forgetful day against the Chiefs two years ago.

“I don’t regret that it happened,” Seumalo said. “I think it made me a better player in focusing [on] things I need to focus on. It’s going to happen the same with Andre. Everybody in the building knows what kind of player he is.”

Playing on the offensive line can be a thankless job. There is often little public recognition. Mistakes are magnified. Seumalo may have had his worst game just two months ago against the Falcons, which had some fans and media again calling for his job. But he has since rebounded with nary an acknowledgment.

Vaitai helped the Eagles win a Super Bowl two years ago when Peters suffered a season-ending injury. But he has struggled in a reserve role. He got blown up by linebacker Shaquem Griffin on a key third-down run Sunday that led to a costly fumbled exchange between Wentz and running back Miles Sanders.

But the Eagles’ offensive line isn’t the only unit around the league to suffer losses.

“Grenades pop off and guys get hurt," Seumalo said. "You got to go with it.”

The Brooks situation only compounded the Eagles’ injury woes. He had astoundingly returned from a January Achilles tendon rupture by the season opener and would become the team’s most reliable blocker. The Eagles, in turn, rewarded him with the long-term investment even though he had another year on his original deal.

But another setback is obvious cause for concern. While Brooks’ anxiety has never caused him to miss more than one game in a row, as those who have dealt with his condition know, there isn’t a cure, only management.

“If anybody’s going to be OK,” Seumalo said, “Brandon’s going to be OK.”