Interim coach Steve Wilks told reporters Monday morning that P.J. Walker is dealing with a high ankle sprain suffered in Thursday night's win over the Atlanta Falcons, thrusting Mayfield back into the starting lineup.
Wilks noted that Walker played through the injury but wouldn't be available against Baltimore. The coach did not indicate Walker's timeline to return but doesn't anticipate the QB going on injured reserve at this point.
Sam Darnold, who returned from an ankle injury, will back up Mayfield.
Mayfield started the first five games of the season but struggled mightily, completing 54.9 percent of his passes for 962 yards with four touchdowns and four interceptions. He suffered an ankle injury of his own in Week 5 that opened the door for Walker to take over the starting role.
Mayfield replaced Walker at halftime of Week 9's blowout loss to Cincinnati and played well, but at the time, Wilks decided to stick with Walker, who has led the Panthers to two of their three victories on the season.
The news means Mayfield will face a familiar foe in Baltimore. The QB started eight games against the Ravens during his four seasons in Cleveland. The Browns went 3-5 in those starts, with Mayfield generating an 83.2 passer rating with 13 TDs to 9 INTs versus Baltimore.