Darriel Mack Jr., who was competing with Brandon Wimbush for the UCF starting quarterback job, broke his ankle this week in a non-football-related activity and is out indefinitely.

"There is no specific timetable for his return. He will not be available for training camp," UCF coach Josh Heupel said in a statement. "We hope Darriel has a speedy recovery, but we are excited about the talent we have in the quarterback room to start the season."

Mack was a backup to McKenzie Milton last season but filled in for Milton after he suffered a devastating season-ending knee injury that will also keep Milton on the sideline for the 2019 season. Mack started three games last season as a redshirt freshman for the Knights, including the 17-point comeback victory over Memphis in the AAC championship game.

Wimbush, a transfer from Notre Dame, heads into the season as UCF's likely starter with redshirt freshman Quadry Jones and true freshman Dillon Gabriel also competing for the job.