LAS VEGAS—It was the quintessential Vegas Golden Knights spectacle, or at least as quintessential as spectacles can get after only one year of existence. Spotlights danced. Snare drums rattled. Sparklers launched next to the mini-medieval castle. A massive barbute descended from the ceiling, forming an entrance tunnel from the home bench. An aerial artist shimmied down a silk ribbon, helping deliver the ceremonial puck to Wayne Newton and Lil' Jon, who also appeared in a hype video alongside Bryce Harper and the Backstreet Boys.

"Are you ready?" the PA announcer bellowed in the most intense tone that a face-palming pun has probably ever received. "Because it's Knight time."

See? Typical pregame Vegas, minus the dramatic battle reenactment. Except then something unusual happened Thursday night at T-Mobile Arena: The hockey team lost. Yes, the Golden Knights were last seen shaking hands with the Capitals on this very ice in June, forced to watch while Alex Ovechkin smooched the Stanley Cup. (That particular defeat stuck with them all summer.) But they had also fallen just 12 times here during their inaugural regular season—10 in regulation, seven by multiple goals, and only three before New Years' Day. The players swarmed, the fans suffocated. It was the one place in town unkind to visitors.

Two fresh banners were hanging when the crowds started spilling in from the Strip: white for winning the Pacific Division, black for the Western Conference championship. It was owner Bill Foley who famously declared that the Golden Knights could reach the playoffs in three years and capture the Stanley Cup in five. He could've earned enough cash to buy another NHL franchise if he had placed a futures bet on that first part—so long were those odds, even after the expansion draft—but their five-game loss to Washington ensured that at least one objective remained entering 2018-19. Still, no team had ever raised that high of a bar this fast.

"Really high," winger Jonathan Marchessault said. "But we're going to stop talking about it … We've got to be more sharp."

It should've been a party in Vegas, the sort enjoyed by the Capitals as they pasted Boston by a touchdown (and extra point) at their banner-raising ceremony. Instead, the Flyers whirled the desert town and whipped the Golden Knights, 5-2, chasing starting goalie Marc-Andre Fleury midway through the second period to spoil the premiere episode of Season 2.

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"Pretty disappointed," coach Gerard Gallant said.

"Obviously very frustrating, being so bad at home," Fleury said.

"I don't know about frustration," forward Pierre-Edouard Bellemare said. "But you're pissed."

As an expansion organization last season, Vegas opened on the road in Dallas. The sparkplug of that night's win, James Neal, departed in free agency. So did fellow second-line mainstay David Perron, replaced wholesale by veterans Max Pacioretty and Paul Stastny. With middle-six forwards Alex Tuch and Cody Eakin injured, and defenseman Nate Schmidt currently training in Austria while serving a now-19-game banned substance suspension, the Golden Knights struggled to cleanly exit pucks from their end and pressure Philadelphia in the neutral zone. MAF was meh, allowing five goals on 16 shots before getting the hook for backup Malcolm Subban. "It's a good reminder," Fleury said. "There's no easy nights, right?"

Eighty-one games remain, of course. Anyone pressing the panic button here should relax with one of those fluorescent mega-slushies (rum optional) on the Strip. But the Golden Knights learned some valuable lessons too. They will be hard-pressed to replicate the magic of last season, from the individual motivation gained upon getting left unprotected in the expansion draft to the collective civic response after the Oct. 1 mass shooting at Mandalay Bay. But most of a Stanley Cup final roster—the only expansion team to ever sniff the playoffs—returned. That was GM George McPhee deciding that this group could do it again, mathematical regressions be damned.

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"We know we're a pretty good team this year," said Marchessault. "but we've got to get back to work."

Marchessault did his job early, slinging a shot from the left faceoff circle to put Vegas ahead 1-0. Then the house lost big. An ill-timed pinch from defenseman Jon Merrill led to a breakaway goal for rookie Oskar Lindblom. Winger Wayne Simmonds struck twice with a total shot distance of nine feet. "Could still win 4-3 in overtime," one scribe remarked along press row, evidently hopeful for a better story. But the Golden Knights never regained their ground. A poorly timed line change sprung defenseman Robert Hagg (three goals in 70 games) for an unimpeded wrister, and Scott Laughton's acrobatic deflection sent Fleury down the tunnel 66 seconds later.

"Chalk that up to a tough night," Gallant said. "Hope we don't see more of them."

Even if they do, which they certainly could—a five-game road trip looms next, including a stiff back-to-back against the past two champs, Washington and Pittsburgh—the Golden Knights are better than this. They'll contend for another title in a cluttered Pacific Division. They'll probably make the playoffs again. At that point, opening night will feel like a distant, forgettable memory. "This isn't the start that we wanted," Bellemare said. "But it's a good slap in the face."