Steelers linebacker Bud Dupree tore his left ACL in Wednesday's 19-14 victory over the Ravens, according to NFL Network's Ian Rapoport.
On Thursday, an MRI reportedly confirmed initial fears of Dupree's injury.
The non-contact injury occurred in the second half of Wednesday's win. Dupree limped off the field following the injury and did not return to the contest.
"I think it was very quiet, very sad, very low, just because having our fellow teammate going down, Bud, and not knowing what's going on over there," Steelers wide receiver JuJu Smith-Schuster said after the game.