Thirty minutes had passed since the unthinkable happened, barely enough time to process the fact that Duke Coach Mike Krzyzewski had just popped his head into the winning locker room to offer his admiration.

So Mercer forward Bud Thomas stood in a cramped hallway within PNC Arena, shaking his head in disbelief as he thumbed through his cellphone. It had never frozen like this before.

“It just keeps saying 20-plus messages,” he said. “I only got to read one of them.”

An upset-filled NCAA tournament received its biggest jolt yet Friday, as No. 14 seed Mercer authored a stunning 78-71 victory over third-seeded Duke in a Midwest Region first-round matchup, wreaking havoc on brackets nationwide and giving March Madness its newest Cinderella story.

It’s the second time in three years Duke has lost to a double-digit seed in its opening game of the NCAA tournament.

Mercer, making its first NCAA tournament appearance since 1985, will face 11th-seeded Tennessee on Sunday in the round of 32 after the Volunteers bested Massachusetts, 86-67, later in the afternoon.

The Bears beat Tennessee in last year’s National Invitation Tournament.

But Friday’s win was no fluke. Not when the Bears had the mighty Blue Devils, playing just a short drive from the school’s campus, on the ropes all afternoon.

Mercer, the Atlantic Sun champion, opened the contest by attempting an alley-oop. It limited Duke stars Jabari Parker and Rodney Hood to 6-of-24 shooting and pulled away down the stretch with an 11-0 run, delighting a crowd that had no problem embracing March’s newest underdog.

This triumph, though, was a year in the making for the only team in the country to start five seniors in every game.

Mercer won the Atlantic Sun regular season title in 2013 only to be relegated to the NIT when Florida Gulf Coast, last year’s NCAA tournament Cinderella, won the conference tournament with an 88-75 win on Mercer’s home floor and advanced to the Sweet 16.

“We were thinking that could be us,” said point guard Anthony White Jr., who hit a three-pointer that tied the score at 63 with 2 minutes 41 seconds remaining after Duke had taken a five-point lead.

The Blue Devils had a rough afternoon. They went more than five minutes without a field goal as Mercer surged down the stretch.

Parker (14 points) and Hood (six points) didn’t find a groove in what could be their last college game, and though District native Quinn Cook finished with a game-high 23 points and guard Rasheed Sulaimon had 18 points — the duo hit 12 of Duke’s 15 three-pointers — the Bears had an answer every time.

Forward Jakob Gollon led a balanced attack with 20 points, including four free throws in the final 11 seconds to ice the game. Big man Daniel Coursey added 17 points and White chipped in 13 .

Their collective moxie came from Coach Bob Hoffman, who remained as confident this week as he was when he asked his wife and college sweetheart, Kelli, out for the first time right after she ended an engagement with another man.

“When we got paired with Duke, right from the beginning, he said, ‘They can be beat,’ ” she said.

Hoffman, 56, stood a few feet away in the bowels of the arena Friday, reflecting on his own winding path to this point.

He began his coaching career as a high school assistant coach more than 33 years ago, and his other jobs included four years as a women’s basketball coach and stops at obscure places like Oklahoma Baptist, Texas-Pan American and the NBA Development League.

He hadn’t previously been a head coach in the NCAA tournament. To the surprise of many, he’s undefeated after Friday.

“It was a special day,” Hoffman said. “It’s a special moment for my wife, my family, just everybody that has continued to stay behind me through the ups and downs we’ve been through.”