Rob Gronkowski is making great progress from offseason back and forearm surgery, but he is unlikely to play in Week 1 for the New England Patriots against the Buffalo Bills.

"It's a huge stretch to think he could play against the Bills," the source said.

Another source said Gronkowski "looks great, is doing great" during his workouts at the Patriots' training facility.

If Gronkowski begins the season on the physically unable to perform list, he would automatically miss at least the first six games.