UFC flyweight prospect Maycee Barber has suffered a complete ACL tear in her left knee, according to her father, Bucky Barber.

Barber's team believes she suffered the injury early in the first round of a decision loss to Roxanne Modafferi at UFC 246 on Saturday, after stepping awkwardly on Modafferi's foot. The injury was obvious in the second round, after Barber reached for her knee in pain after stumbling after a Modafferi punch.

The injury is expected to sideline Barber (8-1) for nine months. Her father anticipates her undergoing surgery in California soon, before rehabbing in Las Vegas.

"We think she injured it in the first 10 seconds," Bucky Barber told ESPN. "She stepped on Roxanne's foot as she backed up and felt a pop. You can see the knee give out on the side. She went back and started fighting and trying to do things and I noticed she was flat in a way I've never seen before."

In a bizarre moment, a ringside physician for the Nevada State Athletic Commission actually checked out Barber's knee between the second and third rounds of the bout. The UFC broadcast picked up the physician informing referee Jason Herzog, "She's got a small, partial ACL tear. She's fine."

Barber, 21, is considered one of the top young prospects in the sport. She has set her sights on becoming the youngest champion in UFC history, a mark currently held by light heavyweight champion Jon Jones, who won the belt when he was 23.

Modafferi's win was a major upset, as she was the largest betting underdog on the UFC 246 card. When ESPN asked Modafferi if she was worried Barber's injury might take anything away from her victory, Modafferi said she hadn't processed it yet.

"I hope she gets better," Modafferi said. "I felt kind of weird. This is the first time I've noticed my opponent have an injury in the fight, so it was bizarre."