The Tar Heels (4-1) admittedly have relied on their transition game this season to offset early struggles in the halfcourt offense. Butler (3-1), however, stripped UNC of those opportunities by dropping both guards once a shot went up on the offensive end.
North Carolina managed just two fast breaks points in the first half and finished with six for the game.
"We were pretty diligent about 1 and 2 getting back, and 3, 4 and 5 ran pretty hard," Butler head coach Brad Stevens said.
Without easy baskets in transition, North Carolina was forced to rely on its halfcourt set to score points. The Bulldogs' man defense was stingy enough to prevent many open looks and the Tar Heels often settled for contested shots.
"They were trying to get all up in us," junior wing Reggie Bullock said. "They were trying to take us out of the things we wanted [to do]. We just can't let teams do that."
UNC shot 32.0 percent (8-of-25) in the opening 20 minutes before finishing at 42.9 percent (27-of-63).
On top of that, Butler played with more toughness and physicality on the defensive end. Sophomore post Desmond Hubert started for North Carolina, but was pulled five minutes into the game and never returned. Freshmen Joel James and Brice Johnson were also pushed around, combining for two rebounds in 23 minutes.
The Bulldogs were physical with James Michael McAdoo, although they were also effective in not allowing him to get the ball where he wanted.
The sophomore, who is not a traditional back-to-the-basket post scorer, attempted to back his man down twice in the first half before losing the ball both times. Other times he appeared hesitant about where to go with the ball once he received an entry pass inside the 3-point circle.
McAdoo's first half line consisted of four points on 2-of-6 shooting, four turnovers and zero rebounds.
That last statistic was not limited to UNC's preseason All-American. North Carolina's four primary post options – McAdoo, Johnson, James and Hubert – combined for two first-half rebounds.
Butler held a 24-12 rebounding edge at halftime, including an 8-1 advantage on the offensive glass. UNC narrowed those margins to 39-29 and 12-10 in the final box score, but that didn't stop Williams from blasting his team's work on the boards.
"When you look at it, last year we led the nation in rebound margin, and this year our rebound margin is probably No. 15 or something like that," Williams said. "They outrebounded us by 12 in the first half. We had one offensive rebound in the whole first half. So, to me, that is aggressiveness, and they showed us."
Butler outscored UNC by 11 in second-chance points (18-7), the same margin as the final score (82-71).
The Bulldogs' defensive game plan resulted in a 29-point lead - 60-31 - with 11:56 to play.
Both coaches stressed different aspects of the game to their team prior to tip. For Williams, one of the three bullet points he wrote on the locker room wipe-off board was "having the best brains" that the Tar Heels have played with all season.
"That shows that you're tough," Williams said. "It shows that you're doing your assignment, regardless how little the assignment may be, you should do that assignment to the best of your ability."
Stevens limited his bullet points to a pair of items.
"The two things that scare you the most about playing a Carolina team is No. 1 transition and No. 2, the defensive glass," Stevens said. "And we did a good job in both of those areas."
The Bulldogs not only excelled in limiting UNC's transition game and controlling the boards, but they also won the toughness battle that Williams highlighted for his team.