Duke basketball and UNC played a thriller in the ACC Tournament at Spectrum Center. Here are the observations.

Kon Knueppel scored 17 points and Duke held off a second half rally by North Carolina to beat its rival for the third time this season, 74-71 on Friday night in Charlotte to reach the Atlantic Coast Conference Tournament championship game.

Duke freshman Cooper Flagg appeared to injure his left ankle after slipping under the basket and was helped to the locker room by two teammates late in the first half. He did not return.

Cooper Flagg and Duke are big favorites to win this week's conference tourney. Clemson, Louisville and Wake Forest are in the mix.

Duke men's basketball finds itself two wins away from claiming its second ACC tournament championship in the last three years. But to play for the title, the top-ranked Blue Devils will first need to take down rival North Carolina on Friday night in the ACC semifinals at the Spectrum Center — likely without leading scorer Cooper Flagg.