With all the intensity his team was lacking at that moment, Williams stormed down the bench, demanding Justin Knox enter the game for a passive Tyler Zeller.
But Zeller didn't need a tongue lashing to know what he'd done wrong.
"[Coach] was more mad at me than anybody, because I wasn't going to the boards hard enough," Zeller acknowledged. "There were a couple of rebounds I should have gotten. John [Henson] was battling with [Jordan] Williams, and that's a tough matchup, so I knew I needed to get in there and work on the boards."
Fortunately for the Tar Heels, the early hook sent exactly the message Williams wanted. After the slow start, Zeller's torrid first half paced Carolina to a 12-point halftime lead they would never relinquish. The junior center hit six of his first 10 shots from the field, ending the half with 14 points in just 12 minutes. By night's end, he had racked up 25 points, an ACC career high in scoring that topped a 24-point performance at Duke, to go along with six rebounds, a block and a steal.
It was an impressive night, made even more so by the fact that Zeller was matched against another top center in Maryland's Williams. In his first two injury-shortened seasons, Zeller often struggled when matched against similarly sized players. But against the Terrapins, he seemed to relish the challenge, showcasing an array of hooks, turnaround jumpers, and aggressive dunks that had many on press row discussing Zeller as a first-team all-ACC candidate.
Despite the fact that the Washington, Indiana native has played far more minutes this season than in his previous two, Zeller says his legs feel fresh.
"We need to knock on wood, but they're good," he said. "You get to this time of year and you're going to have aches and pains. But you have to just keep going. You get more and more motivated as the end of the season comes. You see two more games and the ACC is over. Not long after that, when the season's over, you don't get to play any games. You're just sitting there in the offseason. So it's one of those things that motivates you -- you get your legs back for the end of the season."
In practice, Zeller has been working particularly on establishing lower post position and holding his ground in a range where he can use an increasingly polished set of post moves.
"It's experience," he explained. "You can't post too early or else they're going to push you out. You can't post too late or you won't get the ball. It's one of those things where you just learn your teammates and learn how to do it."
Though Zeller's increasingly consistent offensive production has been a key as the Tar Heels have rattled off 15 wins in their last 17 outings, there's still room for improvement. He can drift through stretches where he fails to establish strong position. Defensively, he sometimes finds himself pinned too deeply under the basket. And as Roy Williams noted after the game, his penchant for getting out on the break sometimes means he's forgetting his rebounding responsibilities -- the mistake that led to the head coach's brief first-half explosion on the sidelines.
But the maturing of Zeller's offensive game, coupled with Henson's shot-blocking prowess on defense, is giving Carolina a powerful one-two punch as the calendar turns to March.
And Zeller says the best is yet to come.
"I definitely know I can play better," he said. "If we win two more games, we can win the ACC. But we've got a long way we can go. Everybody can continue to improve something, and I think we're just going to get better and better."