Backup center Julian Vandervelde underwent back surgery last week, the Eagles said Sunday. Vandervelde had been sidelined for most of training camp, which he entered in a competition with David Molk for the backup spot.
There is no timetable for Vandervelde's return. Guard Dennis Kelly had back surgery last August and missed the first month of the season. There are indications that Vandervelde underwent a similar procedure to repair a damaged disk.
Vandervelde suffered a back injury late last season. Coach Chip Kelly said earlier this summer that this injury was not related to the previous one.
The injury creates an opportunity for Molk, who signed with the Eagles during the offseason. Molk was out of football last season. He was a seventh-round pick by San Diego in 2012 and played 12 games for the Chargers as a rookie.
"The sad thing is this is kind of how the NFL works," Molk said. "Your gain is someone else's [misfortune], which is terrible. It's the business."
Molk took 41 snaps in Friday's preseason loss to the Bears. He will continue to play with the second-team offense.
"I played well," Molk said. "A couple of little mental things, but overall, it was a really good game."
Wide receiver Riley Cooper returned to practice Sunday on a limited basis. Cooper has missed most of training camp and sat out Friday's game because of a foot injury. He participated in individual drills and said he was "feeling a lot better."
"I think the plan right now is to just do individual drills today and reassess tomorrow," said Cooper, who said he didn't know whether he would play in Friday's game against the Patriots. "I felt really good, like I didn't skip a beat. . . . I felt pretty comfortable getting in and out of breaks."
Nose tackle Bennie Logan (hamstring) and wide receiver Jeff Maehl (foot) also returned to practice.
Cornerback Nolan Carroll (hamstring/groin), linebacker Jake Knott (hamstring), and running back Chris Polk (hamstring) continued to miss practice.
Running back Matthew Tucker (hamstring) and linebacker Casey Matthews (back) missed practice after they were hurt in Friday's game. Kelly said he expects both to return Tuesday.
The Eagles will have a walk-through Monday before leaving for New England at 2 p.m. for three days of joint practices with the Patriots.
Kelly said he wanted to use Sunday and Monday for corrections from the Bears game before focusing on the Patriots. Kelly expects Tuesday and Wednesday to be physical practices, with situational work on Thursday.