ORLANDO, Fla. >> UCF quarterback Darriel Mack Jr. broke his ankle and it is unclear when he will be able to resume playing football, the school announced today.

“Quarterback Darriel Mack Jr. suffered a broken ankle from non-football related activity this week and 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 primarily used as a backup to McKenzie Milton, but stepped into the starting role after Milton went down with a season-ending knee injury.

With Milton expected to miss all of the 2019-20 season while recovering from a knee injury that nearly led to the amputation of his leg, Mack was one of four quarterbacks competing for the starting job in the fall along with Notre Dame transfer Brandon Wimbush, redshirt freshman Quadry Jones and true freshman Dillon Gabriel.

Wimbush, who is the most experienced quarterback, now becomes the front-runner to lead the Knights’ offense.

Mack started three games in 2018, including leading Knights’ 17-point second-half comeback against Memphis in the American Athletic Conference Championship Game on Dec. 1. He finished with a 2-1 record, with the only loss coming in the Fiesta Bowl against LSU.

Mack passed for 619 yards and rushed for 337 yards with nine total touchdowns last season.

Wimbush was expected to provide depth and experience at the quarterback position. He chose UCF with no promise of a starting job, but he had high hopes of winning the competition during preseason camp.

Wimbush started 16 games at Notre Dame and became the first quarterback to account for at least 1,000 career rushing yards since Tony Rice in 1988. He finished with 1,156 yards and 16 touchdowns before being replaced in the lineup by Ian Book.

“Brandon’s an old kid. He’s an old kid that gets it,” UCF quarterbacks coach Jeff Lebby said of Wimbush’s perseverance during spring. “He’s played a lot of ball. He’s been through a lot of ups and downs, so he’s had to find ways to continue to bounce back. And I think that’s the biggest thing is you’re getting a guy that’s got this got a lot of history and so that’s been fun to see.”

The Knights could also lean on Gabriel, who arrived as an early enrollee in January.

The three-star prospect from Hawaii who spurned offers from Georgia and USC is the first freshman quarterback signed by Heupel and his staff. Gabriel wrapped up a stellar prep career with a state-record 9,848 passing yards and 105 touchdowns.

Heupel said during the spring he could see the quarterback situation sort itself out during the summer.

“I’ve been through quarterback battles in training camp and every time we’ve had a new one, I don’t think any time in my career did I name a guy as we finished up spring ball,” Heupel said in April. “I do believe strongly in how much players can change, not only at quarterback but at every position, inside your program from the time they finish spring ball until you get them back in training camp.

“I want kids to have to earn it and go prove it as we go through our summer program as well.”