"They've been very mentally tough recently, just showing a lot of resiliency," Harper said. "I think that can only come from confidence. These kids believe they can beat anybody right now. If you can walk out on the court and believe in your heart you can win, you have a chance."
Harper, the successor to late Hall of Fame coach Kay Yow, guided the program to a surprise run to the ACC championship game as a No. 6 seed in 2010. That squad fell to the Blue Devils after a run of four games in four days.
NC State hadn't beaten Duke since upsetting the top-ranked and undefeated Blue Devils in the 2007 tournament semifinals here under Yow. The Wolfpack hadn't beaten a team this highly ranked since that game, either.
But ninth-seeded N.C. State (18-14) built an eight-point lead with about 3 minutes left, then held off a final charge from the top-seeded Blue Devils (24-5).
When the horn sounded, the N.C. State bench spilled onto the court to mob each other in celebration. The Wolfpack advanced to Saturday's semifinals to face No. 15 Georgia Tech, the tournament's fourth seed.
The Wolfpack improved to 6-2 in the ACC tournament under Harper.
"I can't even describe how I feel right now," Kastanek said. "We just did something for the seniors. It's that feeling that I'm not the only one benefiting from this game. My teammates aren't the only ones benefiting from this game. Coach Kellie isn't the only one benefiting. We all are, the people back at N.C. State.
"We just beat Duke - that's a big deal for N.C. State."
Myisha Goodwin-Coleman added 12 points for the Wolfpack, who shot just 39 percent. But N.C. State scored 26 points off 22 turnovers and scored 21 second-chance points to pull off the upset of a team that won the regular-season meeting by 24 points in January.
P "They just did a super job hitting some key shots as a team," Duke coach Joanne P. McCallie said. "It just goes to show that you don't have to shoot a great percentage, you don't have to be all-world, you just have to play with a whole lot of heart. I think that's what they accomplished today."
Chelsea Gray scored a career-high 25 points to the Blue Devils, who cut that eight-point deficit to two in the final seconds. But Gray missed the front end of a 1-and-1 with 2.9 seconds left, and the ball went out of bounds to N.C. State. The Wolfpack inbounded the ball to Goodwin-Coleman to dribble out the final 1.8 seconds and start the celebration.
The Wolfpack entered the tournament with an 0-11 record this year when trailing at halftime. But N.C. State rallied from a 42-35 halftime deficit to Florida State in Thursday's first round and pulled ahead in the final 90 seconds to win 74-71.
On Friday, the Wolfpack trailed 37-36 at the break but never let the Blue Devils put together a big run. Duke's biggest lead was six midway through the second half.
"We kind of relaxed and our defensive intensity slowed a little bit," Gray said. "We got a little comfortable and we just can't do that against good teams."
Goodwin-Coleman hit the go-ahead 3-pointer to make it 64-62 with 6:12 left, and the Wolfpack pushed that lead all the way to 73-65 on a pair of free throws from Kastanek with 2:54 left.
Tricia Liston hit a pair of 3-pointers to cut into the deficit. And when Emili Tasler missed two free throws with 15.9 seconds left, Duke had the ball with a chance to tie it. Gray drove into the paint and drew the foul on Goodwin-Coleman, but her free throw struck the front rim and the ball went out of bounds.
The Blue Devils had reached the tournament semifinals every year since 1995 and appeared to be in the running for a No. 1 seed in the NCAA tournament. But they struggled all day and went 9-for-19 from the free throw line, losing their first tournament opener since falling to Maryland in the 1994 quarterfinals.
It also was the first time in tournament history that the No. 1 seed had failed to reach the semifinals. The No. 1 seed was 32-0 in the tournament against teams seeded eighth or ninth before Friday.
Duke freshman Elizabeth Williams finished with 12 points and a tournament-record seven blocked shots.