Baltimore Ravens star Dennis Pitta has suffered another hip injury, it was announced on Friday.
Tight end Pitta, 31, sustained the injury during Friday's organised team activities, a devastating blow for a player whose career has been threatened by chronic hip issues.
A statement from Ravens general manager Ozzie Newsome read: "This is incredibly disappointing, obviously for Dennis, and for the Ravens.
"Dennis is one of the great Ravens, and he has done everything he can to make our team better."
The Ravens said Super Bowl champion Pitta - who will undergo further tests - was hurt on a non-contact play. He stretched out to make a catch and fell to the ground but could not get up or put weight on his leg afterward.
Pitta, who turns 32 this month, missed the entire 2015 season and most of 2014 and 2013 with serious hip injuries.
He initially dislocated and fractured his right hip in training camp in July 2013 but was able to return for the final four games of that season.
In week three of the 2014 campaign, Pitta dislocated the same hip. That kept him out the rest of the season and all of 2015, and doctors advised him not to continue playing.
But Pitta returned to play in all 16 games for the Ravens last year, leading all NFL tight ends with 86 receptions.