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Villanova didn't do much with its No. 1 seed this week, and the Wildcats may not get another one.

Sterling Gibbs hit a step-back jumper at the buzzer and Seton Hall stunned third-ranked Villanova 64-63 in a thrilling Big East quarterfinal Thursday, a loss that could cost the conference's regular-season champion a top seed in the NCAA tournament.

"You've all heard me say this before: This was not about 1 seeds, 2 seeds. This was about we wanted to come to Madison Square Garden and win the Big East tournament. Winning the Big East tournament would mean much more to us than a 1 seed," Wildcats coach Jay Wright said. "The NCAA tournament seedings, my belief is 1, 2, 3, it doesn't matter that much. You're going to play great teams."

Eugene Teague had 19 points and 12 rebounds for the eighth-seeded Pirates (17-16), who advanced to the Big East semifinals for the first time in 13 years.

Josh Hart scored 18 to lead the top-seeded Wildcats (28-4), beaten only twice in 18 league games this season while winning their first outright Big East title since 1982. Both losses were blowouts by Doug McDermott and Creighton.

Patrik Auda scored all 13 of his points in the first half for Seton Hall, a 10½-point underdog. But the pesky Pirates, accustomed to playing close games, built a 15-point lead and recovered after Villanova spurted past them with a 16-0 run in the second half.

It was Seton Hall's first victory in five tries against top-seeded teams at the Big East tournament.

"That was a great college basketball game," Wright said. "Great to be a part of it. Great atmosphere. The Garden was rocking. We had a lot of fun."

Villanova took a 63-62 lead on Darrun Hilliard's floater in the lane with 7.8 seconds to go. Seton Hall pushed the ball past halfcourt, then called timeout with 3.7 seconds left.

With much of the crowd on its feet, Jaren Sina inbounded and Gibbs backed off Hilliard with a hard step back, draining a 17-foot jumper from the top of the key just as the horn sounded.

"We never really got rattled," Pirates coach Kevin Willard said. "These guys have a lot of heart. They have a lot of character, and they deserve to win."

A fired-up Gibbs, who finished with 10 points, jumped onto the scorer's table and looked up at the crowd as excited teammates ran all over the court in a wild celebration.

"We're really confident, honestly, especially after you beat the No. 3 team in the country," said Gibbs, a sophomore transfer from Texas whose brother was a Pittsburgh star. "We know if we can beat them, we can beat anyone. So we're just up for the challenge."

The shot was a near carbon copy of the one Kemba Walker hit three years ago at the Garden during Connecticut's captivating run to Big East and NCAA tournament championships. That buzzer-beating jumper by Walker, also in the quarterfinals, beat a top-seeded Pittsburgh team that was led by Gibbs' brother, Ashton.

Hilliard scored all 11 of his points in the second half. JayVaughn Pinkston also had 11 for the Wildcats, but the 77 percent free throw shooter was 3 of 10 at the foul line as the Wildcats went 15 for 25 (60 percent) to Seton Hall's 6-for-9 mark.

"The difference between winning and losing is so close," Wright said. "We're a pretty good free throw shooting team. If we made free throws, we might be sitting here talking about a different outcome."

Villanova also shot 37.9 percent from the field and 21.1 percent from 3-point range (4 for 19).

"We got the shots we wanted to. We just weren't making them," guard Ryan Arcidiacono said.

Villanova won both regular-season meetings, by an average of 16.5 points, and figured to have an advantage again after Seton Hall held off Butler 51-50 Wednesday night.

Early on, though, it was the Pirates who looked fresh even though they had little time to rest.

On a bitterly cold day in the Big Apple, the Wildcats took a while to warm up. They missed 13 of their first 14 attempts from 3-point range and trailed 44-31 with 14 minutes remaining. But they made a flurry of steals during a 16-0 run and took their first lead at 47-44 on Hilliard's 3-pointer with 8:03 left.

Fuquan Edwin tied it with a 3 and Teague followed with a three-point play to put the Pirates back in front.

With the score tied at 59, Arcidiacono's steal sent Villanova on a fast break that culminated in Hart's layup with 40 seconds left.

Undeterred, the Pirates worked the ball around and Gibbs passed to Sina for a 3 from the left corner that gave them a 62-61 edge with 17.2 seconds remaining.