LAS VEGAS — What happens in Vegas, stays in Vegas.

Including the idea of raising an NBA Cup banner.

After capturing Adam Silver’s beloved tournament in Tuesday’s 124-113 win over the Spurs, the Knicks decided against a title banner at MSG because they’re “focused on the bigger picture,” The Post learned.

Still, they planned to celebrate the championship before Friday’s home game against the Sixers “in a proper way.”

The decision was a surprise after Mike Brown pumped up his players in Tuesday’s pregame speech by describing a banner in the MSG rafters as a reward. As the coach said in a moment that was caught on TV, “You’re playing for something bigger than you. A banner getting raised in the rafters.”

But the Knicks also entered this campaign with the “singularly focused” goal of winning an NBA championship, not an NBA Cup title, and that became the overriding emotion as the team left Sin City.

They’ll be the first NBA Cup winner not to hang a banner, following the Bucks and Lakers, who did so previously. This can’t be a popular decision in the league office, where Silver has prioritized his tournament as he attempts to beef up interest in the regular season. But the NBA doesn’t have control over banners inside arenas.

And the Knicks, who have banners for division titles, decided against memorializing a midseason tournament in the rafters.

Before Tuesday’s victory, Knicks players were mixed on whether they should hang one.

Mikal Bridges was against it.

“Nah, I’m OK,” Bridges said, adding, “I think you’re searching for something even more than that.”

Mitchell Robinson was gung-ho about it.

“Hang something,” Robinson said, “appreciate us for something.”

OG Anunoby and Josh Hart wanted a banner but were more lukewarm on the idea. Regardless, the players won prize money worth over $500K each.

“They can put a banner up,” said Anunoby, who owns a 2019 NBA championship ring with the Raptors. “But no parade or something [like that].”

Added Hart: “I don’t know. Yeah, why not? Obviously, it’s a Cup, it’s a title. It’s something you want to win. So — yeah, hang a banner. Obviously, there are different standards for those with Cups and Finals. But whenever you want to go out there, you want to win and compete for a title, that’s what you want to do. And you want to celebrate that.”

Turns out, they’ll celebrate the NBA Cup championship — but without the banner.