The Seattle Kraken have yet to play a game in the National Hockey League. On the eve of their debut, five players have already been sidelined by an implacable foe: the league’s Covid-19 protocols.

The team, which plays its first regular season game Tuesday night against the Las Vegas Golden Knights, did not release any details about precisely what caused the players to be deactivated, including whether they tested positive for Covid.

During a call with reporters on Monday, Dave Hakstol, the team’s head coach, was asked why it looked like the team was down four men during a practice. Mr. Hakstol said that four players — Marcus Johansson, Jared McCann, Jamie Oleksiak and Joonas Donskoi — were not on the ice because of Covid protocols. Calle Jarnkrok was already known to be out because of the protocols.

“Things happen quickly, and sometimes at inopportune times there’s different challenges as you go throughout the season,” Mr. Hakstol said. “This is one of them for us early on.”

The coach acknowledged the hurdles posed by the sidelined players. “We have decisions to make as we go through the day,” he said. “We’ll do that and we’ll be ready to play as we get into Vegas tonight and ready to go tomorrow.”

The league’s deputy commissioner, Bill Daly, estimated in September that 98 percent of players will be vaccinated against the virus, leaving just a handful of the league’s 700 players without protection, The Associated Press reported. The Kraken’s general manager, Ron Francis, said at the start of training camp that the team’s entire roster had been vaccinated, according to The A.P.

The N.H.L. released detailed protocols in September that encouraged players to get vaccinated, ideally with a Pfizer-BioNTech or Moderna vaccine. “Quite simply,” the league said, “vaccination is the most effective measure to protect against infection with Covid-19.”

Clubs have the right to suspend an unvaccinated player who is unable to play because of the protocols or local regulations and also dock the player’s salary.