NEW YORK—Following the Blue Devils’ thrilling 81-77 win against Louisville, Duke head coach Mike Krzyzewski’s opening statement effectively summarized what a capacity crowd at the Barclays Center had been treated to Thursday afternoon.

“So that was a quarterfinal game. Holy mackerel,” Krzyzewski said. “We’re so pleased and proud of the win because we beat a heck of a team and a team that could win it all.”

To advance to the ACC championship game for the first time since 2014, the Blue Devils will have to accomplish the same feat barely 24 hours after their Thursday triumph against a team that is playing as well as anyone in the country.

The opponent on the other side of the court will also be wearing a very familiar shade of blue.

Fifth-seeded Duke will take on top-seeded North Carolina for the second time in the past week Friday at 7 p.m. in the first ACC tournament semifinal. Although the Blue Devils will be playing their third game in three days and had to dig deep to eliminate the Cardinals immediately after the Tar Heels opened the postseason by trouncing Miami, Duke played arguably its best game of the season against Louisville.

In addition to getting second-half defensive contributions from freshmen big men Harry Giles and Marques Bolden, the Blue Devils finally got Grayson Allen back on track. Duke has repeatedly said it is trying to mold its identity in real-time this season, and the quarterfinal victory reiterated that Allen playing well can take the team to another level.

But even with Allen’s 14 points against North Carolina last Saturday—granted, the junior was not nearly as effective driving to the hoop as he was against the Cardinals—the Tar Heels made the biggest plays late in a 90-83 win to end the regular season. If Allen can deliver another strong offensive game in the semifinal tilt, the fatigued Blue Devils will still have to find a way to slow down the Tar Heels’ high-powered offense to win the season series.

“Our identity has to be formed around defense. Everyone in the country knows that we can score,” graduate student Amile Jefferson said. “When we play defense and find a way to get stops, we win ballgames.”

Against Louisville, an unlikely switch to zone defense let Duke get the stops it needed to earn a third top-15 win. The Blue Devils (25-8) might try to employ similar tactics and prioritize defending the paint against a bigger Tar Heel team that uses a four-player frontcourt to pummel teams inside and leads the nation in rebounding margin.

But if Duke elects to prevent Isaiah Hicks and company from getting touches in the paint, it will still need to keep track of Tar Heel stars Joel Berry II and Justin Jackson on the perimeter. Berry lit the Blue Devils up with five first-half 3-pointers in the regular-season finale, and the ACC Player of the Year Jackson has the versatility to pour in points for North Carolina (27-6) regardless of a team’s defensive strategy.

“It’s not like we played a great zone, but it changed the tempo,” Krzyzewski said. “And then we went back to man because we didn’t want to give up an open [3-pointer on the last possession].... That was the possession of the game defensively.”

Duke will likely need similar efforts against North Carolina—the same type of performance that earned the Blue Devils an 86-78 win Feb. 9. Freshman Jayson Tatum was the star of the second half of that contest with 19 points in the period to support Allen and the team’s lleading scorer Luke Kennard, and the rookie was tough to stop again Thursday with a vintage performance.

After getting shut down in Duke’s January loss at Louisville, Tatum had 25 points on 9-of-15 shooting, exploiting bigger defenders in a way he will need to Friday for the Blue Devils to avoid losing the season series to its rival for the first time since 2009.

The St. Louis native went just 4-of-13 against the Tar Heels Saturday and will look for a second straight bounce-back performance. He could be joined in the frontcourt for long stretches by his friend and classmate Giles, who scored on his first low-post touch Thursday, threw down a transition dunk off an assist from Tatum and added three rebounds, one block and one steal to spell Jefferson.

“I think he’s worn out,” Krzyzewski said of his co-captain. “He had to play the two big guys from Clemson, and Harry was playing so well that I just felt that one, if he’s playing well, we’ve got a better chance to win. But, two, going forward, to get him time in a game like that was really valuable. And it turned out it was more than just getting him time. He produced.”

The question for Giles and his teammates is whether they can put together two complete performances in back-to-back contests, something they have failed to do since December.

If Duke cannot, it will likely have to watch North Carolina celebrate a third straight berth in the ACC tournament championship game.

But Allen looking energized had the Blue Devils flashing their potential on a big stage again, giving Krzyzewski and his players confidence that they have the weapons to shoot down the Tar Heels.

“He was himself today,” Krzyzewski said of Allen’s 18-point effort. “What he did was sensational. I loved it.”