DURHAM Duke coach Mike Krzyzewski said it wasn't an X and O thing.

Senior guard Nolan Smith - after one of his most spectacular games at Duke - said no mechanical adjustments were necessary.

After trailing by 16 points in the closing seconds of the first half to a determined North Carolina team, No. 5-ranked Duke's players calmed down and dug deep to find the spirit and strength for a 79-73 win against No. 20 North Carolina on Wednesday night at Cameron Indoor Stadium.

"It was all in the head and in the heart," Smith said. "That was the only change."

North Carolina big men Tyler Zeller and John Henson dominated the lane on both ends of the court in the first half as the Tar Heels built a 43-29 halftime lead.

But Smith and Seth Curry answered with brilliant second-half performances as Duke tightened up its defense and outscored North Carolina 50-30 after halftime.

Senior guard Smith scored 22 of his career-high 34 points in the second half, driving for layups and pull-up jumpers, making three 3-pointers and shooting 13-for-23 from the field.

Curry, a sophomore guard, scored all but four of his season-high 22 points in the second half and shot 8-for-12 from the field. The rest of Duke's team shot 7-for-33, but Smith and Curry scored enough to spark the comeback and hold off North Carolina in a game of huge importance in the race for first place in the ACC.

The Blue Devils (22-2, 9-1) increased the distance between themselves and North Carolina (17-6, 7-2) in the ACC standings and broke the Tar Heels' five-game winning streak.

"They keep coming at you, coming at you, coming at you," North Carolina coach Roy Williams said of Duke. "And you have to keep coming back at them."

Krzyzewski said he didn't make any strategic adjustments at halftime. But he spent more time talking to the team than usual. He didn't yell at the players. He tried to calm them.

He told them to chip away at the lead a little at a time, but the Blue Devils tore big chunks off North Carolina's advantage quickly. Smith made a deep 3-pointer as Duke took advantage of some well-timed offensive rebounds to score the first seven points of the second half and draw within seven.

Later, down 54-47, the Blue Devils got seven straight points from Curry as they reeled off 13 of the next 14 points for a 60-55 advantage.

"We were just in a groove in the second half," Curry said. "We were really aggressive and our shots were falling."

Duke, which never led in the first 30 minutes, never trailed after a Ryan Kelly go-ahead 3-pointer with 9:14 remaining.

It was a bitterly disappointing end for an inexperienced North Carolina team that showed courage and maturity after falling 82-50 at Cameron in the final game of the 2010-11 regular season.

The Tar Heels started two freshmen and two sophomores, but relied on Zeller (24 points, 13 rebounds) and Henson (14 points, 12 rebounds) to jam up Duke in the lane, especially early in the game.

The second half was different. North Carolina shot 37.5 percent from the field after halftime, including 0-for-6 from 3-point range. Williams said it would be easy to blame the turnaround on youth, but he didn't want to do that.

"We did have some poise at times," Williams said. "We got the ball where we wanted it at times. But you can't turn it over and give them second shot opportunities."

Duke capitalized on North Carolina's mistakes and shot 50 percent from the field in the second half after being held to 33.3 percent in the first half. Krzyzewski evened his record in college basketball's biggest rivalry at 35-35 and improved to 8-7 against Williams.

Krzyzewski was asked if he preferred winning by 32 last season or by a close margin this season. It didn't make a difference to him.

"A win over an outstanding program is a treasured win, all the time," Krzyzewski said. "... They were as good a team as we've played. No question about it."