SOUTH BEND, Ind. (AP) -- No. 15 Pittsburgh couldn't overcome the combination of poor free-throw shooting and Notre Dame's defense.
The Fighting Irish (No. 17 ESPN/USA Today, No. 16 AP) had a 13-point advantage on free-throw points despite taking just five more shots and held the Panthers to a season-low 31 percent shooting to beat Pittsburgh 81-66 on Sunday.
Notre Dame coach Muffet McGraw, who has been critical of her team's ability to defend shots most of the year, said except for being outrebounded 56-42 it was the best defense her team had played all season.
"A lot of pressure," she said. "We got aggressive with it."
Pittsburgh coach Agnus Berenato said the Panthers missed too many easy shots.
"They made layups and made free throws and Pitt missed layups and missed free throws. That was the game," she said. "Bottom line, you have to make layup and free throws."
The Panthers were just 14-of-27 from the free-throw line.
The Irish (18-5, 6-3 Big East) improved to 17-1 all-time against the Panthers (18-5, 8-2), with the lone loss coming last season at Pittsburgh. The victory was Notre Dame's first against a ranked opponent in five tries this season. It was the first loss in five Big East road games for the Panthers.
The Irish improved to 7-0 this season when they have five players in double figures. They managed that despite its two leading scorers, Charel Allen and Ashley Barlow, being held to six points each because of foul trouble.
"That's what so great about this team. We're so balanced," said Melissa Lechlitner, who finished with 12 points.
Tulyah Gaines led the Irish with 13 points, making 9-of-10 free throws.
Lindsay Schrader added 12 points and eight rebounds for the Irish. Devereaux Peters was leading the Irish with 11 points when she left the game with 13:44 left with an injured left knee. Becca Bruszewski added 10 points each for the Irish.
McGraw said the Irish won't know the extent of the injury to Peters until after she undergoes an MRI exam on Monday.
Marcedes Walker, who missed Pitt's last game with an ankle injury, had 18 points and 14 rebounds. Shavonte Zellous added 16 points and nine rebounds and Xenia Stewart had 16 points.
Walker twice had chances to give Pitt the lead early in the second half, but both times she failed to convert a free throw for three-point plays. The Irish opened a 38-33 lead when Peters made a free throw for a three-point play. She extended the lead to 45-35 moments later when she converted on another three-point play.
McGraw said the victory was important for the Irish, who play three more ranked opponents in the next four games.
"This was just a critical win for us. We absolutely had to have this game to help us in the Big East standings, to help us overall down the road, for our confidence," she said. "We haven't done a good job of protecting our home court, so we really needed this one."