Ian Rapoport of NFL Network reported Jeffery is progressing "according to plan," but he may not be ready for Week 1.
Jeffery underwent surgery to repair a torn rotator cuff after the Eagles' Super Bowl victory over the New England Patriots. Eagles head coach Doug Pederson recently told reporters Jeffery is in the "strength phase" of his rehab.
"He's doing a great job with his rehab," Pederson said. "He is in I would say more the strength phase with the weights and that part. He's still doing his lower body conditioning with running and doing some things that way with his legs, making sure his cardiovascular is good.
"He can't do a ton of stuff yet necessarily on the field because of the motion of the arm swing, but we can get him in the tanks, the pools, the Alter Gs, things like that, and get his cardio up. But kind of in the strength phase right now and really doing a nice job."
Jeffery, 28, recorded 57 receptions for 789 yards and nine touchdowns last season. He played in all 16 regular-season games despite dealing with some lingering injury issues. It was the first time since 2014 he played an entire season.
The Eagles would have to rely more heavily on veteran Mike Wallace and Nelson Agholor if Jeffery misses extended time. They could also increase their two-tight-end sets with Zach Ertz and rookie second-round pick Dallas Goedert.