ST. LOUIS – Awful all night, Harrison Barnes came through when North Carolina needed him most Friday night.

Barnes scored five of his 12 points in overtime and the top-seeded Tar Heels escaped a huge upset with a 73-65 victory against 13th-seeded Ohio in the Midwest Regional semifinals.

Ohio, trying to become the first team seeded 13th or worse to make the regional finals since the NCAA tournament expanded in 1985, had a chance to convert a three-point play that would have given the Bobcats the lead with 25 seconds left in regulation.

But Walter Offutt missed from the line and Ohio went 0 of 6 from the field in the first overtime of this year’s tournament.

“One free throw away,” Offutt said. “As a leader on this team, I take responsibility that I’ve got to hit that free throw. It just feels terrible to kind of let my team down in that sort of way.”

Tyler Zeller finished with 20 points and a career-high 22 rebounds for North Carolina, which sorely missed injured point guard Kendall Marshall. The Tar Heels had three players with double-doubles for the first time in an NCAA tournament game: Reggie Bullock had 17 points and 10 boards, and John Henson had 14 points and 10 rebounds.

Offutt led the Bobcats (29-8) with 26 points, including 18 from 3-point range, and Nick Kellogg added 14. But D.J. Cooper, who averaged 20 points in the first two tournament games, finished with just 10 on 3-of-20 shooting.

North Carolina (32-5), which has won 11 straight in the regional semifinals, will play North Carolina State or Kansas on Sunday.

“It means a heck of a lot,” Coach Roy Williams said moments after the escape, “but we’ve got to play better than we did today.”

The Tar Heels barely advanced without Marshall, perhaps their most irreplaceable player and the steadying hand behind their fast-paced attack. His absence showed.

Williams said he didn’t think Marshall would be able to play Sunday.

“I don’t think so ’cause he still hasn’t done anything, but North Carolina’s going to play on Sunday. We’re happy about that,” he said.

Barnes was dismal, flirting with a season low in scoring as he went 3 of 16, missing from inside, outside and everywhere in between. But his teammates weren’t much better, turning the ball over a season-high 24 times and shooting just 40 percent, six percentage points below their average. Worse, they could never get a handle on the quicker Bobcats.

“Probably the ugliest win I’ve ever been a part of,” Reggie Bullock said. “But we won and hopefully we’ll do better Sunday.”

After trailing by as much as 15 in the first half, Ohio got hot from long range and gave the Tar Heels almost more than they could handle. Ohio, a 10½-point underdog, was 8 of 13 from 3-point range in the second half, with Offutt doing most of the damage. He made a 3-pointer to start a 14-5 run and hit two more during the stretch, which pulled the Bobcats to 42-41 with 10:23 to play.

After Zeller’s layup and a dunk by James Michael McAdoo, Cooper hit his only 3 of the game. Kellogg came back with another to give Ohio its first lead, 47-46, with 8:28 to play, and the Ohio faithful — plus the new fans the underdogs picked up — went into a frenzy.

The teams traded leads, neither able to put the other away. When Barnes missed badly on a 3 with 1:17 to play, the crowd taunted him with chants of “Air-ball! Air-ball!” But Williams could be heard yelling “One stop!” at his team, and the Tar Heels got it when Cooper missed a jumper at the other end.

Bullock then drilled a 3 to give North Carolina a 63-61 lead with 39 seconds left, but Offutt — who else? — scored on an off-balance drive and drew a foul. Offutt’s foul shot was way left, the only free throw the Bobcats missed all night, and Zeller grabbed the rebound.