LAS VEGAS — As the Vegas Golden Knights morph from 500-1 long shots to chic pick to hoist the Stanley Cup, Art Manteris is preparing for an emotional roller coaster unlike any he has encountered in three decades as a professional oddsmaker.

Three weeks into the N.H.L. playoffs, Knights jerseys are as ubiquitous on the Las Vegas Strip as poker chips and frozen margaritas, illustrating the team’s enormous popularity. But as much as Manteris would like to see the Knights bring the Cup to the city, he may be forced to take one of the coldest baths of his career if the expansion team defies the odds.

Station Casinos, where Manteris serves as vice president of race and sports book operations, is staring at a seven-figure liability if the Golden Knights cap their inaugural season by winning the Stanley Cup. The liability is the largest for any futures’ bet accepted by a sportsbook managed by Manteris since he moved to Las Vegas in 1978. A handful of other sportsbooks nearby are expected to incur similar losses on the futures market, producing an overall liability between $5 million and $10 million for casinos in Las Vegas, according to Johnny Avello, the executive director of Wynn Las Vegas’s race and sportsbook.

With the Knights up by two games to one against the San Jose Sharks in their Western Conference semifinal series, sportsbook operators are grappling with a puzzling conundrum. While passionate fans line sportsbooks and bars to cheer on the Knights, the books continue to take a beating when the hometown team takes the ice.