CHAPEL HILL — Outside of that 33-point loss at Florida State on Jan. 14, North Carolina coach Roy Williams has liked his team's defensive effort and intensity. Now he's starting to appreciate the Tar Heels' defensive execution, too.

UNC's 74-52 victory against Clemson at the Smith Center on Saturday wasn't always pretty, and the Tar Heels' defense was a primary reason why. The Tar Heels (23-4, 10-2) held the Tigers (13-13, 5-7) without a field goal during the final 7 minutes, 42 seconds, and UNC held Clemson to 37.5 percent shooting overall.

It was the third consecutive game in which No. 8 North Carolina held its opponent to less than 40 percent shooting, and it continued the Heels' recent trend of defensive improvement. Even when the Tar Heels entered the season as the favorite to win the national title, critics questioned their defense.

Now it's becoming a strength.

"We had the intensity early [in the season]," Williams said. "We just weren't very proficient at it. Everybody thinks that defense is just sweat and slobbering and yelling at guys and stuff like that.

"You've got to know what the dickens you're doing."

The Heels have known recently, at least. Clemson mustered just 22 points in the first half, and three of those came on a 3-pointer from Andre Young at the halftime buzzer. The 22 points were the second-fewest UNC had allowed in a first half this season, edging the 20 the Heels allowed Virginia last week.

When the Tigers weren't missing shots, UNC was often blocking them. The Tar Heels finished with seven blocks - three of them by junior forward John Henson, who also added 13 points and eight rebounds.

Though Williams defended his team's defensive effort from the start of the season to now, Henson said it's the one thing that has most improved.

"I think effort, more than anything," Henson said when asked what has changed with the Heels' defense. "I think we realized that defense can help us win games when we're not hitting shots, and I think that's something that we've taken heed of and we just started playing on defense a lot better."

UNC wasn't particularly sharp offensively during the first half - it shot 41.2 percent - but the Tar Heels' defense and offensive rebounding allowed them to build a 31-22 halftime lead. Clemson, now 0-56 on the road against UNC, trimmed the deficit to six with 11:59 to play, but then went five consecutive possessions without scoring.

Harrison Barnes led the Tar Heels with 24 points and seven rebounds, and Tyler Zeller added 14 points and seven rebounds. Sophomore point guard Kendall Marshall finished with 13 assists - three more than Clemson had as a team.

Barnes scored 14 of his points during the second half and has now scored at least 20 points against Clemson in the past three meetings between the teams. Surrounded by cameras afterward, Barnes said, with a bright smile, "I always have good games against them."

Zeller, who also finished with a block and a steal, tried to explain UNC's recent defensive surge.

"We're getting a lot better containing off the ball, and keeping the ball in front of us," he said. "And then just our team defense is much better. We're rotating, we know that our teammates are going to be there to help us when we do screw up, and then I think effort-wise, we're giving a phenomenal effort for the most of the time."

The defensive effort didn't wane for UNC on Saturday, even with the result long decided. In the final seconds, with the court mostly filled with walk-ons and seldom-used reserves, Clemson's Bernard Sullivan attempted a shot. UNC freshman Desmond Hubert swatted it away, providing a fitting end.

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