This was a familiar experience for North Carolina. The defense slumped early, and Georgia Tech jumped out to a 21-0 lead. First-half struggles were the norm a year ago. The offense scrapped its way back, putting a touchdown on the board just before the half to close to within seven. Larry Fedora’s unit had made a habit of putting up points quickly.

But what happened after that -- the scene on the sideline, the talk in the locker room -- this was all different. This was a North Carolina team ready to move past its demons and get to work.

“No one blinked,” linebacker Jeff Schoettmer said. “No one yelled at each other on the sidelines. At halftime there was no rah-rah speech to be said. We were focused on the mission.”

It’s amazing the difference a year -- and a new defensive coordinator -- can make. North Carolina trailed at the half in 10 of its 13 games a year ago as focus wavered and the defense muddled its way through one ugly performance after another. And when things went bad, they went very bad.

Everything about this season feels different though, Schoettmer said. The Tar Heels dominated the second half against Georgia Tech, forcing two turnovers and outscoring the Yellow Jackets 24-10 en route to a momentous come-from-behind win on the road.

“You don’t know the personality of your team until you’ve encountered enough ups and downs on game day,” defensive coordinator Gene Chizik said. “We’re at the point where there’s enough scenarios -- Georgia Tech is a great example -- where we have to battle and fight and claw and scratch our way back into the game. Players and coaches didn’t panic.”

There are two major changes happening on D at North Carolina. The first is schematic, and Chizik’s game plan built around core concepts and tight coverages has made a world of difference. The second, however, is cultural, and that’s had an even bigger impact.

“The No. 1 thing contributing to this [success] is our team chemistry,” Schoettmer said. “That was one of our issues last year. Last year, if we were down 21, I don’t think there’s a chance we would’ve come back and won. Guys believed in each other and stayed tight.”

With largely the same talent pool that made up one of the nation’s worst defenses a year ago, Chizik is finding instant success in 2015 with a group willing to work together. The message, he told them before the season, is that 11 good players doing their job are far more effective than one great player doing his.

So during team meetings, the defense watches film, and any mistakes by an individual player are highlights. That player is then asked to explain what happened, to account for his errors. It’s created a level of accountability from individual players and also a better understanding of how each man’s role affects the larger goals of the team.

“There’s got to be a relentless desire to win your box, to do exactly what you’re supposed to do on every play,” Chizik said.

A quick review of the results:

Last year, UNC was outscored by 104 points in the first half, largely due to the defensive woes. This season, Chizik has cut opponents’ completion percentage from 60 percent to 43 percent and trimmed their yards-per-pass by half.

Overall, North Carolina has trimmed nearly a yard-and-a-half per play off its average from a year ago.

Opponents are averaging just 1.6 points per drive against UNC this year, down from 2.6 last season

Last year’s D allowed conversions on a whopping 38 percent of third-and-longs. This year, that number has nearly been cut in half.

And as Chizik reviews the film, he’s certain of one thing.

“We’ve not played great defense,” he said. “We’ve played improved defense.”

The brilliance of Chizik’s scheme is in its simplicity, allowing adjustments to happen on the fly. He’s taught defensive concepts that can be implemented between series, and he’s empowered his players to take ownership of their performance when it happens. This isn’t rocket science, and that’s what makes it work.

“We don’t reinvent the wheel during games, but we have base foundations and concepts that are applicable to different things offenses can do to you,” Chizik said. “Our goal was to build enough concepts that it allows you to make adjustments they can understand in the heat of the moment.”

Again, the numbers are startling. North Carolina is allowing just 4.7 yards-per-play in the second halves of games (down from 6.0 last year). Last season, drives that included at least one explosive play (runs of 10 or more yards, passes of 20 or more) resulted in points 52 percent of the time. This year, opponents are scoring on just 27 percent. The UNC defense hasn’t allowed a single point following a turnover by the offense this year.

The differences are stark, and while the job isn’t done, Chizik said his unit is making strides every week.

A year ago, things were bleak at North Carolina. Now, the ACC Coastal Division seems well within reach, and a defense that was the laughingstock of the ACC is suddenly a force to be reckoned with.

“We’ve improved definitely, but we definitely aren’t where we think we can get to,” Schoettmer said. “[Chizik] has done a great job with us so far. We’ve really bought into what he’s teaching.”