CHARLOTTE, N.C. -- Panthers backup quarterback Sam Darnold, who lost the starting job to Baker Mayfield earlier in the week, departed Friday night's preseason finale against Buffalo on a golf cart after suffering a left ankle injury late in the third quarter.

A league source said Darnold suffered a high ankle sprain and will undergo an MRI on Saturday morning to determine the severity of it. Such injuries typically require four to six weeks of recovery.

"I can't give you any timelines," coach Matt Rhule said after his team's 21-0 win. "We believe it's not a fracture. Hoping that it's an ankle sprain.''

It marked the second time in a week the Panthers lost a quarterback in a preseason game. Third-round pick Matt Corral suffered a season-ending Lisfranc tear in last Friday's preseason loss at New England.

If Darnold's injury is serious, the Panthers would be down to two quarterbacks -- Mayfield and former XFL star PJ Walker -- heading into the Sept. 11 opener against the Cleveland Browns.

The Panthers planned to keep three quarterbacks earlier in camp, with Corral expected to be the third behind Mayfield and Darnold. Corral's injury changed the mindset to keeping two, but Darnold's injury could force another adjustment.

"We'll have to wait and see,'' Rhule said. "Sam's a tough kid. He usually comes back really quickly. I'd say nothing's off the table.''

Darnold was hit from behind by Buffalo defensive tackle C.J. Brewer while running to his right to throw the ball away. Brewer's body appeared to roll over Darnold's ankle.

Darnold stayed down for several minutes before being helped into a golf cart and leaving the field.

Mayfield started and completed 9 of 15 passes for 89 yards and two touchdowns in a quarter and a half for a passer rating of 116.4.

"He did a nice job of moving the football,'' Rhule said. "The thing I like about Baker right now is he plays so steady. You can't tell after every play if it was a drop or a completion. I can't say anything about his footwork, but I thought he made good checks and got us in the right play.''

Mayfield felt he left plenty of room for improvement.

"Some good, some bad,'' he said. "Overall, a little sloppy to be honest with you. I feel like my feet weren't really calm. I felt like I drifted in the pocket a little bit and created my own pressure.''

Mayfield called Darnold's injury "very unfortunate.''

"We're praying for him, thinking about him,'' he said. "It seemed like he was in good spirits for the most part. You never want to see that with anybody, especially your teammates.''

Darnold was 5-for-11 for 48 yards. He also had a 1-yard touchdown run in the third quarter to make it 21-0.

The Panthers acquired Darnold last year in a trade with the New York Jets. He went 4-7 as the starter in 2021.

Carolina brought back 2015 NFL MVP Cam Newton last year while Darnold dealt with a shoulder injury. Newton, Carolina's top pick in the 2011 draft, went 0-5.

Rhule didn't want to speculate on whether the team would consider Newton, who remains unsigned, if Darnold is out for an extended period.

"You know my feelings on Cam,'' Rhule said. "I thought my time with him was fantastic. Probably too early to say much about that.''

Carolina acquired Mayfield in a July trade with Cleveland, which moved on from the 2018 first overall pick after acquiring Deshaun Watson from Houston.

Mayfield and Darnold, the third pick of the 2018 draft, had what the team called an open competition for the starting job that became Mayfield's on Monday.

Carolina also saw kicker Zane Gonzalez leave on a cart with a groin injury suffered while kicking into the net on the sideline. Gonzalez suffered a season-ending quad injury last year at Buffalo in December.

Rhule said the team would look at other kickers if Gonzalez's injury is serious. Punter Johnny Hekker kicked an extra point after Gonzalez left.