The Pittsburgh Steelers fear defensive end Stephon Tuitt tore his biceps - which would end his season - during Sunday's victory over the Cleveland Browns, ESPN's Adam Schefter reports.
Tuitt signed a six-year contract extension worth $61 million on Saturday.
He'll undergo an MRI on Monday.
Tuitt recorded 37 tackles, four sacks, and two forced fumbles in 14 games last season.
It would be a crushing loss for the Steelers' defense if Tuitt misses significant time with the injury.