The Eagles’ Andre Dillard suffered a season-ending biceps injury during Thursday’s practice, NFL sources said.

The left tackle will be placed on injured reserve and undergo surgery. Jason Peters will take over Dillard’s spot with the first team and move back to his long-time position. Matt Pryor will replace the 38-year-old Peters, who was re-signed last month to play right guard.

Dillard suffered a shoulder strain last week and missed a few practices, but he returned Wednesday. Coach Doug Pederson praised the 2019 top draft pick’s performance until that point and said that the 20 pounds he added in the offseason had increased his strength.

“I’ve been real impressed, obviously, with Dillard and his growth, obviously his strength and what he did this offseason coming into camp mentally and physically prepared,” Pederson said. “He’s done a really nice job for us. He has really stepped in and embraced that role at left tackle.”

But Dillard had a bad moment later in the day when defensive end Joe Ostman bull-rushed him back into quarterback Carson Wentz, who was briefly bent over. Wentz got up immediately and was fine. Dillard rebounded and had a decent practice.

Overall, though, the 24-year-old had been up and down in workouts and there was internal concern that he wouldn’t be able to consistently protect Wentz’s blindside once the season began. The Eagles were committed to ride the wave having invested first- and fourth-round picks to move up to select the Washington State product.

Still, a sure future Hall of Famer loomed. Last week, Dillard was asked if there was additional pressure having to replace Peters.

“Well, sure, there’s a lot of pressure and responsibility. You can’t really dwell on that, you know? I’m the guy for the position,” Dillard said. “I’m going to keep proving that I’m the guy for the spot.”

Dillard said his confidence had grown exponentially since last season. The Eagles had concerns about his mental makeup during his rookie season. Dillard started three games for the injured Peters last season and struggled, but a one-start stint at right tackle proved disastrous and he was pulled at the half.

Peters would finish the season once he returned from a knee injury. But he has played only roughly 65% of snaps over the last three seasons. The Eagles and Peters opted to part ways when free agency opened in March. He had hoped to sign with another team as a left tackle.

But weeks passed and then Brandon Brooks tore his Achilles tendon while training in June. A month later, the Eagles brought back Peters, a nine-time Pro Bowler, for a 17th season. But to play guard. The Eagles wouldn’t say it, but it was also as insurance should Dillard falter.

An injury will keep the team from knowing for another year whether Dillard has what it takes to be a starting left tackle in the NFL. They have a cast of other candidates. Pryor has played backup right tackle when he hasn’t been at guard in camp. Jordan Mailata has backed up Dillard, but the former rugby player is still a work in progress.

Mailata may earn the reserve swing tackle spot by default. The Dillard and Brooks injuries had weakened the Eagles’ depth on the offensive line -- an area in which they are typically among the strongest in the NFL. Halapoulivaati Vaitai, who previously was the Eagles’ sixth man, left in free agency this offseason.

The Eagles did draft two offensive linemen this year -- Jack Driscoll and Prince Tega Wanogho. Both have mostly played tackle in camp. Center/guard Nate Herbig is also on the roster and is expected to make the team before Sept. 13′s season opener at Washington.