The Hall of Fame coach then had to endure one stomach-turning play after another in a dramatic and confusing finish that left the Tar Heels in a familiar spot: the NCAA tournament's round of 16.
Tyler Zeller scored 23 points, Harrison Barnes added 22 and North Carolina survived a closing minute that included numerous questionable calls to beat Washington 86-83 in the East region. The Tar Heels are into the second weekend for a record 24th time.
"I told the kids to take care of the old man and they did a good job," Williams said. "I feel a heck of a lot better now."
Rallying from deficits of 11 points in the first half and five in the second, the second-seeded Tar Heels (28-7) went ahead for good on Barnes' 3-pointer with 4:06 left.
But they needed two late free throws from Dexter Strickland and two defensive stops in the final second to advance to play the Syracuse-Marquette winner Friday in Newark, N.J.
"For our lack of experience," Barnes said, "we make up for that with heart."
Terrence Ross scored 19 points and Matthew Bryan-Amaning added 14 for the seventh-seeded Huskies (24-11), who couldn't overcome a subpar game from star guard Isaiah Thomas and a hostile crowd to pull the upset in a fast-paced game full of entertaining plays and mental miscues.
"All of our guys fought and did so many things right that could have enabled us to win the ballgame," coach Lorenzo Romar said, "but we didn't get it done."
Washington, which came in with as many NCAA tournament wins (18) as North Carolina has Final Four appearances, nearly pulled off a dramatic comeback in a virtual road game 2,800 miles from home.
Washington got within 84-83 on Ross' 3-pointer with 17.3 seconds left before North Carolina's Kendall Marshall — who set a school NCAA tournament record with 14 assists — missed the front end of a 1-and-1 at the foul line.
Washington's Venoy Overton then missed a runner in the lane, but the ball bounced off North Carolina and out of bounds with 7.4 seconds left. On the inbound play, 6-foot-10 John Henson knocked away Justin Holiday's pass under the basket and the ball landed in Strickland's hands, and he hit two free throws with 5.4 seconds left.
Moments later, Overton launched a premature halfcourt shot with about 3 seconds remaining that fell well short. Romar indicated that Overton was anticipating getting fouled, something Williams said the Tar Heels planned to do to prevent a tying 3-point attempt.
That wasn't the end of it, though. Not at all.
Instead of letting the errant shot go harmlessly out of bounds, Henson touched the ball on the way down to give the Huskies yet another chance.
"I told John I wished he just caught that ball," Williams said.
But how much time was left?
Replays with the official game clock superimposed on the screen showed there should have been 1.1 or 1.2 seconds to go, giving Washington more time for a final shot. Romar said after the game that his staff asked the referees to review how much time should have been left, but the officials stuck with half a second.
"There's always a lag time between the time the play occurs and the whistle is blown and the clock stops," official Doug Shows told a pool reporter. "By rule, the clock stops when the whistle blows. We were asked to check the time and we verified that it was accurate with the standby official and the clock operator."
Needing to hurry, the Huskies then inbounded the ball to Thomas, who unloaded a shot from the corner. Henson inexplicably touched the ball just before it would have hit the rim and the Washington bench erupted for a goaltending call — not that it would have mattered.
It turned out Thomas had his foot on the 3-point line.
"I kind of felt like it was going to be short because I had to fade away and had to get if off quickly," Thomas said. "I might have had my left foot on the line."
It was a frustrating end to a frustrating day for the star of the Pac-10 tournament. With Strickland in Thomas' jersey all game, the dynamic point guard finished with 12 points and eight assists on 5-of-15 shooting for Washington.
"It's not like they did anything out of the ordinary," Thomas said. "I just didn't make shots that I usually make."
Ross, coming in averaging 7.7 points, tried to pick up the slack by hitting 7 of 10 shots, but it wasn't enough.
Two years removed from a national championship, North Carolina won its 25th straight NCAA tournament game in its home state a year after being relegated to the NIT.
A little stomach bug couldn't hide Williams' smile.
"Last year was very difficult, the most difficult year of my career," Williams said. "But this team has handled a lot of adversity. It feels fantastic."