Chapel Hill, N.C. — After winning a game it probably should have lost, No. 20 Duke now might have to deal with the loss of another seemingly irreplaceable player.

Guard Matt Jones sprained his left ankle early in the Blue Devils' 74-73 upset of No. 5 North Carolina.

And once the euphoria of that most unlikely fifth straight win wears off, a harsh reality could set in: Starting with a rematch at No. 18 Louisville on Saturday, Duke might have to press forward with more captains that are injured than are healthy.

Team spokesman Cory Walton said Thursday that there were no updates on Jones' condition. Immediately after the game, coach Mike Krzyzewski said he "really sprained his ankle pretty badly.

"I'm not sure how long he'll be out," Krzyzewski added.

The junior guard was on crutches on the bench during the second half while Duke (20-6, 9-4 Atlantic Coast Conference) went with just five players for virtually all of the final 25-plus minutes of a game they trailed by eight with less than 7 minutes to play.

"As far as toughness down the stretch, fighting fatigue, fighting the numbers that we had — we made a short bench even shorter when Matt went down," guard Grayson Allen said. "Really, really tough game. Can't be more proud of how we played."

The Blue Devils already were down to essentially a six-man rotation after key forward Amile Jefferson — Jones' roommate and a fellow co-captain — broke his right foot in December.

Duke lost three straight and four of five in January as it learned how to play without him, but once the Blue Devils figured things out, they reeled off four straight wins — including two in a row over Top 25 teams — entering their first meeting with the Tar Heels.

Then came the injury to Jones, one of just two players to start every game, one who averages nearly 12 points and has a team-best 59 3-pointers. He landed awkwardly after an off-balance shot from the corner with 7:43 left in the first half. He was helped off the floor by two teammates and couldn't seem to put any weight on that ankle.

Freshman Luke Kennard replaced him at that point, and the Blue Devils made just two substitutions the rest of the game. Little-used freshman Chase Jeter came in with 14:05 to play when big man Marshall Plumlee picked up his fourth foul, and Plumlee came back in for Jeter with 10:51 to go.

Allen and freshman Brandon Ingram played 40 minutes while freshman point guard Derryck Thornton — who blocked the Tar Heels' final shot — logged 39. Plumlee had 35, including that extended end-of-game stretch with four fouls.

At times, Duke had four freshmen on the floor along with Allen, a sophomore.

"Who were we going to sub?" Krzyzewski asked with a smile. "I mean, that's it, man. I've been saying that since Amile. But they're getting better. They've really gotten better."

It's one thing to ride the short-term jolt of adrenaline that comes with in the immediate aftermath of losing a key player while facing a fierce rival in its noisy arena.

A lengthy absence for Jones would further test a Duke team that now finds itself one game behind ACC co-leaders Miami and North Carolina.

If that winds up being the case, though, that's a challenge they embrace.

"I think we have a lot of guys who are fighters, and even if they miss some shots, even if they get tired, even if they get banged and bruised, they're going to keep fighting," said Plumlee, Duke's last healthy captain. "And I'm so proud of my teammates. I love them."