UNC trailed 73-70 with two minutes remaining when Brandon Watkins robbed Julius Peppers in the backcourt.
Forward Titus Ivory hit a jump shot after the turnover to put the Nittany Lions ahead 75-70 with 1:30 to go. The sequence followed a possession in which Penn State grabbed two offensive rebounds and ran 1:28 off the clock before scoring.
"The Tar Heels didn't have time to recover from the 1-2 punch. I thought our guys really hustled," Penn State coach Jerry Dunn said. "This team is a blue-collar team -- we're overmatched most of the time at different positions.
"But I felt that possession was characteristic of what this team is all about."
The Nittany Lions (21-11) took that blue-collar approach on defense, making one of the nation's best inside-outside offenses one-dimensional.
Peppers and center Brendan Haywood, who combined for 27 points on 12-for-14 shooting in UNC's 70-48 first-round win against Princeton, again had their way down low.
Peppers notched his first-career double-double with 21 points (on 8-for-9 shooting) and 10 rebounds, and Haywood added 13 and 13.
But the Tar Heels (26-7) got nothing on the perimeter, shooting 3-for-17 from 3-point range. Jon Crispin and Ivory took turns guarding UNC star Joseph Forte and held him to fewer than 10 points for just the second time all season.
Forte managed a season-low six points on
3-for-13 shooting. He was 0-for-6 from 3-point range and didn't attempt a foul shot.
Forte was passive with the ball, either unable to beat his man or unwilling to try. The yearlong tug of war -- his critics saying he took bad shots and too many of them -- finally began to affect him. He glided for 35 minutes as he so often had throughout the season, but the difference this time was that he got nothing done.
"You don't want to be a hog ball or anything of that nature," said Forte, who admitted he limited his shot attempts. "I was trying to get my teammates involved as much as possible, moreso on the inside and a little more on the perimeter, than I usually did in the past."
To get the day's news and headlines in your inbox each morning, sign up for our email newsletters.
Crispin was so focused on stopping Forte that he ended up shooting like him. He scored five points on a 2-for-11 effort, and his brother Joe made only 7 of 21 on his way to 21 points.
But with 21 points from Ivory, 19 points from center Gyasi Cline-Heard and lots of help from the Tar Heels, it was enough.
Enough to send the Tar Heels, who once owned an 18-game winning streak and the nation's top ranking, home.
Enough to make them feel disappointed even with those accomplishments.
"I want to win the whole thing. It's hard for me to sit here and feel satisfied right now," Doherty said. "As you put distance between a loss, you do get to see a bigger picture. The only thing I can tell you is that I gave it my best effort."
The Sports Editor can be reached at firstname.lastname@example.org.