UNC’s Harrison Barnes and James Michael McAdoo crash the boards along with U-Va.’s Akil Mitchell (No. 25) and Darion Atkins on Saturday at the Dean Dome in Chapel Hill. (Grant Halverson/Getty Images)

When Virginia sophomore forward Akil Mitchell missed a layup attempt midway through the second half Saturday at No. 5 North Carolina, the Tar Heels grabbed the rebound, tossed a transition pass nearly the length of the floor and scored on an uncontested layup.

The sequence lasted five seconds, and several Cavaliers players had yet to cross midcourt by its conclusion.

By the time the final horn sounded on 19th-ranked Virginia’s 70-52 loss, its foul-plagued players were exhausted, Coach Tony Bennett was exasperated and the Cavaliers, for perhaps the first time this season, appeared thoroughly defeated.

“As the game wore on, we got tired, and it affected us mentally with our execution,” Bennett said. “I thought we got — soft is not the right word, but just we didn’t have the same kind of toughness and focus that was required and that we had early. We have to learn to play in that situation.”

The Cavaliers (19-5, 6-4 ACC) previously had not allowed a conference opponent to score more than 61 points this season, and their four previous losses had come by a combined 10 points.

North Carolina (21-4, 8-2) owned a considerable size advantage, which it utilized for a 52-32 rebounding edge. Virginia could not contain Tyler Zeller, North Carolina’s 7-foot center who finished with a game-high 25 points and nine rebounds.

“We’ve played against trees like that before,” Mitchell said. “When you get in foul trouble, and he’s putting you under the rim, there’s not much you can really do about it.”

Foul trouble was the origin of the Cavaliers’ struggles — four of Virginia’s top six players had at least two fouls before halftime — and things deteriorated from there.

Fifth-year senior forward Mike Scott, the Cavaliers’ leading scorer and rebounder, sat out the final nine minutes of the first half after picking up his second foul. Mitchell rode the bench nearly the final five minutes of the opening period. Freshman forward Darion Atkins recorded his third foul with just less than three minutes remaining before the break, but at that point, Bennett had little choice other than to leave him in.

Bennett acknowledged afterward that his team missed 7-footer Assane Sene more on Saturday than it had at any previous point in the three weeks since the senior center went down with an ankle injury. At the very least, Sene would have represented five more available fouls.

Initially, the Cavaliers survived their predicament with a four-guard lineup directed by junior guard Jontel Evans’s effective lane penetration. But as Virginia’s foul trouble persisted, its big men grew hesitant in the paint and North Carolina’s rebounding advantage swelled.

“For us to have a chance in a game like this, we’ve got to do a better job on the glass, and for whatever reason, we struggled,” Bennett said. “We tried to work at it in preparing for them, but it was alarming how many second shots, or third shots, they got in a possession.”

Evans described the Cavaliers as “lackadaisical” and “lukewarm” in the second half. It was no coincidence, then, that the Tar Heels executed a 22-5 run that spanned half the closing period.

“We couldn’t keep them off the boards,” said Scott, who finished with a team-high 18 points. “It killed us.”