Virginia center Jay Huff had a clear path to the basket late in the second half against Florida State on Friday when forward Mfiondu Kabengele, seemingly out of nowhere, swooped in to block the 7-footer's layup attempt into the hands of Florida State teammate Trent Forrest.
R.J. Barrett came down with a rebound off a missed UNC three at the other end and was fouled, but he missed both free throws with 13 seconds left to give the Tar Heels a chance to hit a game victor.
North Carolina led by 13 in the first half and 71-67 with less than three minutes left but couldn't hold on.
The Tar Heels shot just 40 percent, including 4 of 27 from 3-point range, against Duke's aggressive defense that played tough after UNC landed an early flurry for the lead. Trailing 73-72 with 32 seconds remaining, Williamson missed a contested shot in the post but beat everyone off the floor with a second jump and tipped in his own miss.
Phil Cofer had 11 points and 7-foot-3 center Christ Koumadje added nine points and nine rebounds for the Seminoles, who will play the victor of No. 3 North Carolina/No. 5 Duke on Saturday night.
"It was tough watching the first few games, watching my brothers out there battling".
2 team in the country, won both games against the No. 3 Blue Devils earlier this season, however Duke was without Williamson for almost all of those bouts.
However, there were a lot of uncharacteristic things that happened in that game that gave me hope the Noles could pull off the upset. It was another sign that Duke, with Williamson back, is closer to being the version that spent a national-best seven weeks at No. 1 in the AP Top 25 this season.
Zion Williamson's return to the Duke Blue Devils' lineup has been nothing short of awe-inspiring, his every whim cross-inspected by ball fans anxious an injury could derail the promise of a storied National Basketball Association career.
UNC: The Tar Heels had claimed their first regular-season sweep of the Blue Devils since 2009, a year that ended with Roy Williams claiming his second NCAA championship.
Florida State comes into this one with a 27-6 mark overall.
Virginia will now await whether they will be a #1 seed in the NCAA Tournament.
This is the 66th ACC tournament but the first semifinals to showcase three top-five Associated Press teams: No. 2 Virginia, No. 3 North Carolina and No. 5 Duke.