"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.