Mayfield added that the fracture in the non-throwing shoulder is "preventing his rotator cuff from firing."
"I need that fracture to heal for me to get back out there," Mayfield said shortly before Cleveland's 17-14 victory against the Denver Broncos on Thursday night. He added that he's hoping to return for Cleveland's game against the Steelers on Oct. 31.
Mayfield suffered the torn labrum in Week 2, but he aggravated the injury in Sunday's loss to Arizona. After Cardinals defensive end J.J. Watt drove Mayfield's left shoulder into the turf, Mayfield stayed down for several minutes before coming back in to finish the game.
Mayfield practiced Tuesday and vowed to play against Denver. But he was ruled out on Wednesday, and backup Case Keenum was announced as the starter.
"If I am not able to ... be 100 percent, that is where I would be out," Mayfield said before Tuesday's practice. "I have to make that decision. Only I know how my body feels. If anyone questions whether I'm hindering the team and going out there injured, that's just not right. It's my decision. I get to say whether I am able to play or not, and that's just how it is."