This is when you know the night hasn’t gone as well as you had hoped on your home floor: from 40 rows up, as the final seconds ticked away, you could hear St. John’s players congratulate Xavier players. You could hear the high fives on the Musketeers bench.

And you certainly could hear the final buzzer as it groaned like an angry foghorn, chasing the remnants of 6,707 to their trains and to their cars, to an icy night made chillier by the final score: Xavier 65, St. John’s 53, made colder by a harsh truth: the Johnnies are probably on the wrong side of the NCAA Tournament bubble.

For the moment, anyway.

“The greatest challenge in sports is sustaining level of effort,” St. John’s coach Steve Lavin said later on, after Xavier had beaten his team for a second time, a fact that will be duly noted if, as expected, the two teams find themselves in a pool of Big East teams wrestling for a final few slots on Selection Sunday in 18 days.

“Teams have off nights. We’ve played at a high level of basketball for a number of weeks. Until tonight.”

The crowd kept waiting for the Johnnies (18-11 overall, 8-8 in the league) to make the kind of second-half run that had routed Butler a week earlier, that had thrown a scare into Villanova in Philadelphia only three days before.

But that’s an example of just how fickle the NCAA fence can be in February. A the Johnnies were jousting with the Wildcats for 36 minutes Saturday, the narrative was practically viral: this is one of the hottest teams in the country, a dangerous team for anyone to face in March, one that’s practically daring the committee to leave it home. They were the sport’s darlings.

Then Ryan Arcidiacono made a 3-pointer, the Johnnies couldn’t grab a rebound, they accepted their attaboys and their get-em-next-times and their keep-your-head-ups … and came out flat as a Kansas prairie against Xavier.

Darlings no more. It happens that fast.

“They did what they wanted inside,” Phil Greene IV said, speaking specifically of Musketeer freshman Jalen Reynolds, who crushed the Johnnies with career highs of 17 points and 16 rebounds in 29 bruising minutes. “Lots of layups and dunks.”

On the other end St. John’s was disjointed and out of sync, shooting 36.7 percent overall, 12.5 percent from 3, 53.8 percent from the foul line. Add them together and it’s a fine OPS for baseball; for basketball it’s a recipe for a humbling.

Maybe St. John’s was due for one of those; since the 0-5 conference start the players had embraced the notion of every game being a survive-and-advance test of their will, and that can take a toll. So can Orlando Sanchez missing the Nova game for a joyful occasion, to be with his wife for the birth of their first child, and Rysheed Jordan missing a practice for a sorrowful reason, because of a murder in his family.

“Most unusual week of my career,” Lavin said.