GREENSBORO, N.C. – Dez Wells gave the floor a hard slap, and No. 2 Duke certainly felt it.
It knocked the Blue Devils out of the Atlantic Coast Conference tournament early — and maybe off the No. 1 seed line for the NCAA tournament, too.
Wells scored a career-high 30 points and Maryland upset Duke 83-74 on Friday night in the ACC tournament quarterfinals.
Wells was 9 of 13 from the field and 10 of 10 from the free throw line to lead the seventh-seeded Terrapins (22-11), who delivered the first big shocker of the week in Greensboro and will play third-seeded North Carolina on Saturday in their first semifinal appearance since 2009.
"You have to be good and be lucky to beat a great team. We're a little bit of both," Maryland coach Mark Turgeon said. "Watching them play tonight I think they fully expected to win that game and that's a good feeling when you have such a young basketball team to play on such a big stage in such a big game and to play with the poise that they played tonight."
They never trailed, held the league's best team from 3-point range to 4-of-25 shooting from beyond the arc, and bolstered their NCAA tournament credentials by beating Duke for the second straight time.
"One of the things during this time of the year ... is that if you lose, it's final," coach Mike Krzyzewski said. "Our team did not feel that. And now we have to understand that that's the way it is. I mean, if you don't do it, it's done. I don't care what your record was, or whatever. It's over. It's one and done."
Mason Plumlee had 19 points to lead the second-seeded Blue Devils (27-5), whose quest for a No. 1 seed in the field of 68 took a jolt.
They had the ball trailing by six points with about 2 minutes left after Seth Curry hit a rare 3-pointer and the Blue Devils got an even rarer defensive stop.
But Tyler Thornton missed 3-pointers on consecutive trips downcourt and Wells and Seth Allen followed with two free throws apiece, with Allen's stretching the lead to 77-67 with 1:44 left.
Duke didn't get closer than five the rest of the way.
"They seemed to always have an answer," Plumlee said, "and that's how they kept us from getting back in the game."
Four Maryland players finished with 10 points apiece — Nick Faust, Jake Layman, Alex Len and Allen. The Terrapins outrebounded Duke by 10 and made 23 of 25 free throws.
They also had the most dominant player on the floor in Wells, who surpassed his previous high of 25 points set in December against George Mason.
In the process, he delivered his team's biggest statement during the run that put the Terps well on their way to the win. Immediately after the 7-foot-1 Len buried an unlikely 15-foot jumper, Wells gave the floor a hard slap — a jab at the Blue Devils' we-mean-business trademark on defense.
"I was trying to energize my guys, and at that moment I was thinking, 'We have to get a stop,'" Wells said. "Whatever I have to do to get my guys pumped. No shots at Duke or anything like that. I just wanted to get my guys energized."
Whatever the motivation, it worked: Curry missed a 3-pointer a few seconds later.
Rasheed Sulaimon had 16 points and Curry finished with 15 for the Blue Devils, who won the tournament the last three times it was played in Greensboro — in 2006, 2010 and 2011.
But they've also lost two straight games in a building that had been their home away from Cameron.
The Greensboro Coliseum was also the site of their one-and-done loss to 15th-seeded Lehigh in their NCAA tournament opener last year. They lost for the first time this season with Ryan Kelly in the lineup; they were 9-4, with an 83-81 loss at Maryland last month, while the power forward was out with a right foot injury.
And their quest to become the fourth program with 2,000 victories will have to wait — this loss leaves them at 1,998.
After missing nine of their first 10 3-pointers, they finally started to warm up in the second half.
Curry — who was scoreless in the first half — converted a four-point play to spark a run that brought the Blue Devils within one. Kelly's three-point play with 13:41 left pulled Duke to 45-44 — the closest it had been since the opening tip.
But Duke had serious trouble stopping the Terps, who scored on 12 of 17 trips downcourt and used an 18-6 run to stretch the lead back out to 13. Pe'Shon Howard's free throw with 5:47 left put Maryland up 65-52.
The teams split the regular-season series, with each winning on its home court. Duke pulled away late to rout the Terrapins by 20 on Jan. 26, before Maryland sprung their previous upset of the then-No. 2 Blue Devils three weeks later in one of Plumlee's worst games of the season.
The third meeting was dominated by the Terrapins, from the tip to the final buzzer.
And Wells was particularly unstoppable. He scored three times over Kelly, dunking on him once and contorting himself for two layups around the fellow Raleigh native, on his way to 16 points in the opening 20 minutes.
"We didn't match their energy from the start," Curry said.
Follow Joedy McCreary on Twitter at (at)JoedyAP