HARTFORD, Conn. (AP) -- Pittsburgh's Xenia Stewart says she's been reluctant to take 3-point shots in a big spot.
That wasn't the case Sunday.
Stewart's 3 with 56 seconds left helped Pitt break open a close game and upset Notre Dame (No. 15 ESPN/USA Today, No. 9 AP) 64-53 Sunday in the second-round of the Big East Tournament.
"I didn't feel like I was contributing enough to my team," Stewart said. "They just told me to look for my shot and that's all it took."
Marcedes Walker had 18 points and 13 rebounds to lead the Panthers (22-9).
Charel Allen had 17 points for Notre Dame (23-8).
The teams combined for 39 turnovers and neither shot better than 35 percent in a defensive struggle. The fourth-seeded Irish came in averaging more than 77 points per game.
Pitt trailed 35-30 early in the second half before going on an 11-2 run.
"They really believed that we could play," Pitt coach Agnus Berenato said. "They rallied."
Allen led the Irish back, and they went up 49-48 with 3:05 left.
A layup by Walker with 1:36 remaining gave Pitt a 53-51 advantage. After Allen missed a jumper on the other end, Stewart hit her big 3-pointer. The Panthers made their free throws down the stretch to earn the school's first berth in the conference semifinals.
The Panthers will play Monday against top-ranked Connecticut.
Pitt started slowly and the Irish went on 14-2 run to open the game.
The Panthers had just two points and eight turnovers in the first 8 minutes. They hit just two of their first 19 shots, and didn't score their second basket until almost the 10-minute mark of the first half when Stewart knocked down a short jumper.
Walker, who had 20 points and seven rebounds in Pitt's first-round win over Villanova, picked up two early offensive fouls, but still had eight of Pittsburgh's first 12 points.
She led the Panthers on a 15-3 run to tie the game at 17. Shavonte Zellous put back her own miss to pull the Panthers within 22-21 at the half.
"They never gave up and they never stopped," Berenato said.
Zellous, who came in averaging almost 19 points per game, went just 3-for-14 from the field.
Allen was 7-of-15 for Notre Dame, which shot just 30.6 percent for the game.
"It's really disappointing for us," Notre Dame coach Muffet McGraw said. "We never really got going."
The Fighting Irish beat the Panthers 81-66 on Feb. 10 in South Bend and came in with a 17-1 record against Pitt.