"Dolphins coach Tony Sparano said on Sunday that Pro-Bowl left tackle Jake Long has been placed on the physically unable to perform list while he attempts to recover from a knee injury.

Long has spent Miami's first three practices of the preseason going through various rehab exercises. His return his unclear, but Sparano said he hopes that Long can be ready to play in the Sept. 12 season opener against New England.

"As I said the other day, he's going to return when I think he's ready to return," Sparano said. "So it's going to be a little while. I'm going to take it really slow with Jake."

If Long isn't off the physically unable to perform list by the start of the season, he'd be forced to miss the Dolphins' first five games. Long has been dealing with knee issues since before the start of the 2010 season."