Pittsburgh quarterback Eli Holstein was carted off the field and taken to a hospital with an air cast on his left leg in the first quarter of Saturday's eventual 37-9 loss at Louisville.
Holstein appeared to have his leg rolled up on when Cardinals defensive lineman Ashton Gillotte sacked him on the second drive of the game.
Nate Yarnell, who started when Holstein missed last week's game against Clemson with a concussion, replaced him Saturday.
Holstein, a transfer from Alabama, won the starting quarterback job over Yarnell during fall practice and helped lead the Panthers to a 7-0 start.