With his second-seeded Tar Heels locked in a semi-tight game late, there were a few times Williams stared off into space rather than look at his players on the floor.
That's a lot of discontent for an NCAA Tournament win.
And in the end, that's what it was: a 102-87 victory against No. 15 seed Long Island, albeit with a few blemishes.
"I'm not pleased with the way we played," Williams said, "but I'm pleased we're still playing.
The less-than-stellar parts aside - like 18 turnovers and 3-for-17 3-point shooting - Carolina's big scorers had an even bigger night.
Throughout the second half, it seemed to be a race to see who would end up as the high-score.
For a while, the leader was John Henson, who had 20 at halftime and 26 a little more than three minutes into the second half as he helped the Tar Heels score 13 of the first 16 points after the break to open up a 21-point lead.
He finished with a career-high 28 points, nine more than his previous best.
Freshman Harrison Barnes, who already binged last weekend with 40 points in an ACC Tournament win, put in 24 points.
But it was the slowest starter, Tyler Zeller, who ended up filling the box score best.
Despite scoring just seven in the first half, the junior forward finished with a career-high 32 points, serving as the go-to scoring option for Carolina (27-7) when the going got tough in the second half.
He did a lot of his damage at the line, where he hit 14 of 19 shots, tying a Carolina NCAA Tournament record for free-throw attempts. It was the most points scored by a Tar Heel in NCAA Tournament play since Tyler Hansbrough had 33 against Michigan State in 2007.
"We knew from the beginning we were the bigger team," freshman point guard Kendall Marshall said. "So we wanted to keep going inside."
It was the first time Carolina had three players score more than 20 points in a game since 2009 and the first time since 1972 that the Heels had a pair of 25-plus scorers in the same NCAA Tournament game.
Marshall's 10 assists - he had just two turnovers - were the most by a Tar Heel in an NCAA Tournament game since Ed Cota hit that mark in 2000.
Barnes also recorded a career-high with 16 rebounds while Henson tied a UNC tourney record with six blocked shots.
All sounds great, right?
Williams and the Tar Heels probably would have felt better about all of that had the Blackbirds (27-6) - who like to get out in transition as much as Carolina does - not been so successful scoring.
Especially off of Carolina's turnovers.
A prime example came just before halftime, when Barnes attempted a long pass that was picked off and converted into a 3-pointer at the buzzer that cut UNC's halftime lead to 53-42.
"You can't have mental lapses," Barnes said. "And we had a few of those today."
Long Island took advantage best it could.
In the first half, that meant a 12-0 LIU run to tie the game at 33. In the second half, UNC allowed a 9-0 run after building its biggest lead, 21 points.
"You get up by 10 or 15 in a regular-season game, and they might just go away," Zeller said. "But this is their last game. In an NCAA Tournament game, they're going to come back even harder."
That's a reality most of the Tar Heels are learning on the fly.
Before this game, UNC's roster boasted a combined 50 minutes of NCAA Tournament game action. All of them belonged to just two players: Zeller and Justin Watts. And most of those minutes were from a first-round game in 2009.
At least when the Blackbirds cut into the lead, the Tar Heels were steady enough to remember one thing: their size advantage.
Shortly after that second-half LIU run, Carolina went to Zeller for 11 straight points. It didn't allow them to pull away, but it was enough to keep the Blackbirds at bay.
This time of year, that's all you can ask for sometimes.