It wasn't a coincidence that UNC had better defensive numbers in-conference than Washington State this season. Carolina can play defense, and when slowed down and forced into an unsteady half-court offense, they can make it up on the other end of the court.
The Cougars never got into a rhythm, going 2 for 16 from behind the arc, and rarely getting a second crack at the basket, with only seven offensive rebounds. And what do you know? When you play at he pace WSU does, it's rather hard to come back from twenty points down[*]. Even with 11:45 to play.