DAYTON, OHIO ? From perfect to pummeled.

Saint Joseph’s first game as the nation’s No. 1 team also was its first loss of the season, a shocking 87-67 collapse against unranked Xavier in the Atlantic-10 quarterfinals Thursday.

The Hawks came in with a 27-0 record, three victories from becoming the first team since 1991 to enter the NCAA Tournament undefeated. But they trailed Xavier by as many as 37 points, and the stunning result raises questions about how serious a contender the tiny Philadelphia school will be for the national championship.

The rout also tarnishes a magical run by a team that was one of the biggest surprises in sports this year, and it could cost Saint Joseph’s a top seeding in the NCAAs.

“I’m assuming that the televisions wherever that committee is meeting didn’t work,” Hawks coach Phil Martelli said.

“This was our 20th game away from our own fieldhouse. We’re 19-1 in those games. They (the committee) will understand that. The committee will do us right because of our body of work. Not 40 minutes.”

It’s the worst loss ever by a No. 1 team against an unranked team and equals the seventh-biggest loss by a top-ranked team against anyone. A partisan crowd began rubbing it in midway through the second half, chanting “Sloppy Joe’s!”

Romain Sato led Xavier with 24 points and 11 rebounds, Lionel Chalmers scored 23, and Anthony Myles had 19.

Saint Joseph’s backcourt standouts Jameer Nelson and Delonte West were held to a combined 11-for-35 shooting and scored 16 points each. Xavier (21-10) made 71.1 percent of its shots while holding Saint Joseph’s to 35.4 percent — its worst showing all season.

Saint Joseph's Jameer Nelson sits dejectedly on the bench near the end of the Hawks' 87-67 loss to Xavier. The loss Thursday in the quarterfinals of the Atlantic 10 tournament in Dayton, Ohio, was the Hawks' first this season.

“Any loss is devastating, especially when you work so hard,” Nelson said. “We take pride in our defense, and we let ourselves down with our defense today.”

Saint Joseph’s, which took the No. 1 spot Monday after Stanford’s loss to Washington, was limited to one field goal during a stretch of more than 10 minutes. And the Hawks’ biggest weakness, their inside game, was exposed by the Musketeers, who outrebounded Saint Joseph’s 43-18.

“They’re a great team. They didn’t go 27-0 for no reason. They made history,” Chalmers said. “They’re one of the great teams in the country. They deserve a No. 1 seed.”

Chalmers added that he thought the Musketeers actually might have done the Hawks a favor.

“It might be better for them to lose early on,” he said. “It might help them in the tournament.”

Playing less than an hour from its campus, Xavier will face George Washington — a 79-50 winner over Rhode Island — in the semifinals tonight.