Washington coach Jay Gruden wouldn't go into any specifics regarding Culliver's injury after practice.
"He hurt his knee a little bit out there," Gruden told reporters. "He jumped up for the ball, landed on it."
Culliver, who was battling a shoulder injury heading into Thursday's practice, is done for the season. He signed a four-year, $32 million contract in March. He had 16 tackles and one pass deflection in his six games for the 'Skins this season.