By Adam Lucas

Oh Roy Williams , you tough little nut.

There's a belief about Williams that he has so much success against N.C. State because he gets so emotional about the rivalry. He lived through the era when the Wolfpack regularly beat the Tar Heels, and even now—it's now a good forty years later—he still has painful memories of those days.

Sometimes, that emotion helps. New Tar Heels don't always understand the ferocity of the Carolina-State game, and Williams is always ready to demonstrate it to them.

Saturday, however, he didn't beat the Wolfpack with emotion. He beat them with a chalkboard.

Williams and his coaching staff ( C.B. McGrath had the scouting assignment on the Pack) tweaked the way Carolina defended the ball screen, which was State's primary method for generating offense for the Atlantic Coast Conference's leading scorer, Cat Barber.

Typically, the Tar Heels have used a hard hedge against the ball screen, meaning the big man jumps out and tries to push the ballhandler backwards. On Saturday, however, Williams made an adjustment, and asked his big men to “flat” the ball screen, meaning they just tried to string Barber out sideways long enough to allow the defensive guard to get back into the play.

“We knew we had to stop the ball,” said Joel Berry, who along with Nate Britt got most of the defensive possessions against Barber. “If their big guys step out to the three-point line, they aren't going to shoot a three. The ball was the problem. So working with the flat screen was good for us because it stopped the ball and made him give it to someone else.”

You think it worked? Here are the stats from the 67-55 victory:

Barber was 4-for-11 in the game, finishing with nine points. It was his first single-digit scoring game of the season.

He was 0-for-3 in the second half, when his team scored just 26 total points.

He attempted just two free throws after coming into the afternoon taking 8.7 free throws per game.

Those 11 field goal attempts might sound impressive, but Barber came into the game having launched 19.9 shots per game in State's previous four ACC contests. Carolina didn't just keep him from scoring. They kept him from being involved at all (Barber also entered the game third in the league in assists; he had just one against the Tar Heels while committing five turnovers).

The crowning moment came early in the second half, when Carolina was surging and Mark Gottfried called his second timeout of the period to try and stem the momentum. On his way to the bench, Barber started barking at a teammate. Coaches intervened. But that was exactly what Britt (“The only one who gave us a chance in the first half,” according to Williams) and Berry needed to see in order to know they were having an impact.

“I could hear some yelling with him and some of his teammates,” Berry said. “As a player and a defender, I love to see my opponent like that because it means he's frustrated. That gives me the confidence to keep doing what I'm doing.”

Carolina could afford to flat the ball screen because Barber isn't necessarily a huge threat to come off the screen and launch a 22-foot three-point jumper. He's much more likely to dart into the lane and either score or get fouled.

But this is a new Tar Heel defensive team. This time, the guards and big men worked together perfectly around the perimeter, keeping Barber out of the paint and forcing other Wolfpack players to beat them. No one was capable of doing it, and after being taken out of his game, Barber mostly looked disinterested in the final minutes of the second half.

Britt and Berry are going to get most of the individual attention for limiting Barber. But it was a cohesive team effort that really did it.

“Our bigs were more aware of where he was on the floor,” Britt said. “We did a good job working as a team. The two players defending the ball screen worked together, and that was key. We stressed a lot going into this game that bigs would have to help us on ball screens to contain Cat, and that's what they did.”

The defense mattered because Carolina's offense was subpar, with the combination of Brice Johnson , Marcus Paige and Justin Jackson managing just 15 points. This was the type of game where an outmanned opponent could have snuck out a win if they'd gotten hot, but the Tar Heels never let that happen.

This year's team has occasionally won pretty, putting up buckets of points and highlight-reel plays. This wasn't one of those games. This was one of those you have to win eventually in every conference season, when the baskets don't fall and you have to figure out another way to win.

As he assessed his team's defensive performance against Barber, Williams mentioned Britt. He named Berry. He praised his big men for playing the ball screen better.