Anthony Gill bows in prayer as Virginia staffers check on Coach Tony Bennett, who collapsed shortly before halftime. He returned to the game after intermission. (John McDonnell/The Washington Post)

The biggest scare Virginia had in its first-round NCAA tournament game Thursday had nothing to do with the threat of an upset by No. 16 seed Hampton — or with basketball at all.

All was well on the court as the top-seeded Cavaliers plodded toward an 81-45 blowout at PNC Arena, but they withstood drama just off court when their coach, Tony Bennett, collapsed on the sideline just before halftime.

After staying on the ground for a brief period, Bennett walked to the locker room with team physicians while his team finished playing out the remaining 30 seconds or so of the half. Bennett, who said he has been “under the weather” lately, told reporters after the game that he fell because he was dehydrated and stood up too fast from his crouching position. He returned for the game’s second half and coached while sitting on a stool.

“I just grayed out or blacked out a little bit,” Bennett said. “. . . I’ve had more Powerade than I’ve ever had in my life right now — I’m hopefully hydrated well. That’s happened before, where you get up quick and you’re a little dizzy, but I don’t know.”

Anthony Gill scored 19 points to lead the Cavaliers, who shot 55 percent from the field. (John McDonnell/The Washington Post)

Bennett also said his doctors mentioned he had a vasovagal reaction, defined by the Mayo Clinic as a drop in heart rate and blood pressure that can lead to fainting.

“I don’t think it’s anything too serious,” Bennett added. “A little more embarrassing than anything.”

The Cavaliers (27-7) will face No. 9 seed Butler in the second round of the Midwest Region on Saturday. The Bulldogs defeated Texas Tech, 71-61, earlier Thursday.

Virginia’s postgame mood was light despite Bennett’s scare. Anthony Gill, who was seen praying over Bennett at halftime, joked he was the one who healed his coach.

Virginia led 40-21 at halftime, and Hampton didn’t get any closer in the second half of a game in which the Cavaliers shot 55 percent compared with Hampton’s 30 percent. Gill led the team with 19 points, seven rebounds and a career-high four assists, and London Perrantes added 12, all of them coming on three-pointers.

The margin of victory, 36 points, was Virginia’s largest in an NCAA tournament game, and its 12 three-pointers also were a program tournament high. The Cavaliers’ reserves contributed 33 points (led by Marial Shayok with 10), their most since Virginia’s first game of the season against Morgan State. Malcolm Brogdon came out of the game with just over nine minutes remaining, and Perrantes and Gill followed about four minutes later.

“I think [bench play] is the most important thing coming into the tournament,” said Brogdon, who had 11 points. Strong play by the reserves “is huge, especially for our first game. We need our guys to come off the bench to play with confidence going forward. I think most of the time the teams that have the best bench production, whether that’s getting stops or producing on the offensive end, I think they end up winning a lot more games than the teams that don’t.”

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The game was competitive — if dictated by a crawling Virginia pace — until the end of the first half, when the Cavaliers made five three-pointers in the final 5 minutes 30 seconds. Hampton’s Quinton Chievous scored the Pirates’ final bucket of the half with 2:08 to play. Evan Nolte sank a three-pointer and Gill added a layup and free throw to widen Virginia’s advantage.

Chievous led the Pirates (21-11) with 17 points, but his game was largely ineffective against the bigger, more physical Cavaliers. Hampton — whose tallest starter, forward Dionte Adams, is 6 feet 7 — was outmatched at every position and could not consistently solve Virginia’s pack-line defense.

“I don’t think that film does them justice, and I say that because of the caliber of competition that they have to play against every night,” Hampton Coach Edward Joyner said. “. . . You say, ‘We’re going to make them beat us,’ or ‘We’re going to make them do this.’ You forget they’re talented kids. They’re ACC-caliber kids for a reason. They actually got the ball in areas where we said, ‘Let’s go see if they can hit that,’ and they hit it.

“As gifted as they are defensively, when you don’t have to see them every night, you kind of forget how well some of them kids can play offensively when given the opportunity.”