NEW YORK -- Duke was 80 minutes from jumping right back to the forefront of the discussion for the nation's best team. The Blue Devils had been clicking on all cylinders for the past month, switching to a zone defense and getting more consistent point guard play.

An ACC tournament title would have refilled the bandwagon for the nation's most talented team -- and the team that was ranked preseason No. 1 by most outlets in October.

And while it didn't all come crashing down in Brooklyn, the Blue Devils' old demons are beginning to surface again.

Duke was bounced from the ACC tournament on Friday by North Carolina 74-69. The deficit grew as big as 16 late in the second half, but the Tar Heels didn't make a field goal for the final 5:33 and Duke had multiple chances to tie the game.

Losing by five on a neutral court to a team that will end up being a 2-seed or better isn't anything to be concerned about. North Carolina had already beaten Duke once this season and had a 10-point halftime lead in Durham just a week ago. But the midseason concerns are still there for the Blue Devils.

Heading into Friday, Duke had held eight straight opponents under one point per possession -- not coincidentally, it had been eight games since the Blue Devils switched from a predominantly man-to-man defense to a 2-3 zone. Because Duke plays with multiple big men on the court at the same time, the Blue Devils had issues defending teams, especially on ball screens away from the rim. The zone enabled Duke to protect the rim and force teams to shoot from the perimeter as opposed to attacking off the dribble.

But North Carolina did whatever it wanted Friday, getting paint touches consistently through either Theo Pinson or Luke Maye. Grayson Allen and Trevon Duval were too spread out at the top of the zone, and the Tar Heels essentially had open entries into the foul-line area.

"Defensively, me and Tre [Duval] up top needed to do a little bit better job of trying to keep it out of the middle," Allen said.

Both Notre Dame on Thursday and North Carolina on Friday found consistent openings in Duke's zone, but neither team could hit shots from the perimeter. The Fighting Irish shot 5-for-23 from behind the arc, while North Carolina was 7-for-24.

According to SportVU, North Carolina shot 42 jumpers Friday -- and only seven of them were contested by Duke. The Tar Heels had 16 layup or dunk attempts. Notre Dame had similar uncontested numbers and created exactly 16 layup or dunk attempts, as well. Granted, both teams have the personnel to cause problems for the Duke zone, with Maye, Pinson and Bonzie Colson all capable of hitting midrange shots or taking a dribble and finding a teammate.

Mike Krzyzewski downplayed North Carolina's success against the zone.

"If we were playing man and they shot 18 out of 24 from 3, then you'd be asking, 'Why didn't you defend the 3 better?'" Krzyzewski said. "But holding them to 74 points was good. They're one of the explosive teams, as explosive as anybody. And they have two kids that can really handle the ball well in the middle of the zone in Pinson and Maye. So that's good for us. The two games we played here, Colson can do that, too, so we got a chance to work our zone against probably two of the best teams that would work against us, and we gave up 70 and 74 points.

"The zone wasn't bad. ... It wasn't great, but it wasn't bad."

Offensively, Duke struggled to get much scoring production from the point of attack. Duval was hampered by an ankle injury he suffered in the first half and still managed to finish with seven assists and five turnovers. But he also didn’t score a point in his 30 minutes on the floor, going 0-for-6 from the field. In the past six games, Duval has totaled 29 points -- shooting 4-for-16 from behind the arc.

In a half-court setting, teams are allowing Duval to shoot perimeter jumpers. He's struggling to get into the lane and create off the bounce as a result.

It wasn't just Duval, though. Duke was sloppy, turning the ball over 18 times -- leading to 21 points off turnovers for North Carolina. Turnovers have been a major issue in many of Duke's losses this season. The Blue Devils coughed it up 18 times against Virginia Tech in February, 18 times against St. John's at Madison Square Garden and 16 times in the loss to Virginia in late January.

"We're not going to win a game against a team of that caliber if we turn it over 18 times," Krzyzewski said after Friday's game.

"We can't turn it over like that," he added later.

Duke's ceiling is still as high as anyone's in college basketball, and the Blue Devils will still be a popular national title pick starting Sunday.

But they still have flaws, and as much as those flaws were masked over the past month, Friday brought some of Duke's demons back to the surface.