DURHAM, N.C. — Duke quarterback Sean Renfree wears blue and white with old school white stripes on the shoulders and No. 19 on his chest.

You might say that as he took the field at Wallace Wade Stadium on Saturday, he looked like the old Baltimore Colt Johnny Unitas. By the end of the game against Georgia Tech, his stat sheet was looking like Johnny U, too.

Renfree completed 26 of 42 passes for 250 yards and four passing touchdowns, tying his career high. He was 4-for-4 in the red zone, was not sacked and threw only one — albeit a fatal — interception.

Still, Tech’s gaps in coverage made it hard to assess Renfree or his numbers. Was he a throwback or just a thrower enjoying an afternoon without defenders in his face or on his targets?

For Tech coach Paul Johnson the answer was simple. Renfree was throwing to receivers who often weren’t covered.

“You’ve got try to make him hold the ball a little bit,” Johnson said after Tech’s 38-31 victory. “You gotta cover somebody a little bit.”

Johnson was asked, “You mean they weren’t covering even a little bit?”

“At times, it looked like it,” he said.

Given that review, it’s no small irony that the victory was sealed by an interception. Still Jemea Thomas, sophomore defensive back who made the saving grab, agreed with his coach.

“As a secondary, we’ve got to improve,” he said.

Duke was running pick routes, and the coverage wasn’t adjusting, sometimes leaving Duke receivers on their own, he said.

But after seeing 41 passes from Renfree, Tech’s secondary did improve just in time to stop a late fourth-quarter Duke drive that would have tied the game.

Thomas, who earlier contributed to Tech’s defensive struggles with a penalty for pass interference, said he made an adjustment that led to his interception. On the interference call, he said, he tried to block the receiver’s hands. On the interception, he turned and played the ball intended for Cooper Helfet, the Duke tight end who already had six catches and two touchdowns.

While Tech’s secondary struggled, Duke’s passing success wasn’t all its fault. Renfree was throwing to a pair of the ACC’s top receivers, Conner Vernon and Donovan Varner, a senior playing his last home game.

The so-called “Killer V’s” combined for 14 catches and 137 yards and two touchdowns.

“They were very good,” Thomas said. “Don’t give them nothing because they’ll take it all from you.”

It also didn’t help that Duke’s quarterback often had plenty of time to find his targets. Tech’s defensive rush often wasn’t one. Johnson said the defensive line wasn’t the problem. He said Renfree has a quick release, and he sets up so deep that “even when they weren’t blocking them, they couldn’t get there.”

Thomas was glad that day of big Duke catches ended with his own. “We started out rough, and we just ended it with a pick,” he said.