GREENSBORO — P.J. Hairston is the lynchpin of the smaller lineup that turned North Carolina’s season around, an outside shooter asked to play power forward, with surprisingly successful results.

So what happens if Hairston can’t play Saturday?

Hairston needed eight stitches in his left hand late Friday night after tearing the webbing between two of his fingers during the second half of the Tar Heels’ 83-62 ACC quarterfinal win against Florida State, leaving his status very much in doubt and leaving North Carolina coach Roy Williams with some serious thinking to do overnight.

“We are extremely concerned right now,” Williams said. “His hand is torn up. They’re stitching it up.”

And his status for Saturday’s semifinal against Maryland?

“We have no idea,” Williams said.

It wouldn’t be a North Carolina postseason without a strange injury to a key player. From Ty Lawson’s ankle in 2008 to his toe in 2009 to John Henson’s elbow and knee and Kendall Marshall’s wrist (and, as it turned out, elbow) last season, the Tar Heels have been in this position before. Now they face the absence of Hairston, whose insertion into the lineup was merely the most critical moment of their season.

The Tar Heels went to Hairston because their young big men were ineffective playing alongside James Michael McAdoo, and going to a four-guard offense created opportunities both on the perimeter and for McAdoo.

Hairston, meanwhile, saved North Carolina’s bacon early in Friday’s game, his 3-point shooting making up for the Tar Heels’ defensive deficiencies inside as the Seminoles piled up a first-half edge on the boards, in the paint and at the free-throw line.

The Tar Heels pulled away in the second half despite McAdoo being anchored to the bench in foul trouble and Hairston jamming his left shoulder in a collision with a Florida State player. And then, late in the second half, with the outcome no longer in doubt, Hairston ran to the bench clutching his hand, leaving a trail of blood on the court.

The ball apparently wedged between the middle and ring fingers of his left hand, splitting his hand open. Teammate Dexter Strickland joked earlier this year that Hairston can be “a little dramatic with his injuries,” but there was nothing contrived about the pain Hairston was in.

Suddenly, the formula that has brought North Carolina so much success in the second half of the season might need to be put on the shelf. “We could play Marcus at power forward, possibly,” Williams joked, gesturing toward 157-pound point guard Marcus Paige. “Conventional wisdom would say you have to go back big, because you can’t teach Reggie the out-of-bounds plays from the ‘4’ spot between now and tomorrow 3 p.m. It’s ridiculous that it’s already midnight and we have to be back here to play a game at 3.”

Big didn’t work for North Carolina earlier this season, which is how Williams ended up with this unusual but effective lineup in the first place. For a coach who likes to have two workhorse big men, he has a shortage of them. There’s McAdoo, who had 12 points Friday, and the list ends there.

Desmond Hubert struggles on offense, Brice Johnson struggles on defense and Joel James and Jackson Simmons have limitations as well. But with so little time to prepare for Saturday’s semifinal, if Hairston can’t play, the Tar Heels will have no choice but to go back to a lineup that didn’t work for them before and hope it works now, with a chance to play for the ACC title on the line.

DeCock: ldecock@newsobserver.com, @LukeDeCock, (919) 829-8947