TAMPA, Fla. -- NHL commissioner Gary Bettman said the league has only four unvaccinated players as it opens up the 2021-22 season.

Bettman was in attendance for the regular-season opener as the Pittsburgh Penguins beat the back-to-back Stanley Cup champion Tampa Bay Lightning 6-2 on Tuesday night.

"Everybody banding together to do the right thing," Bettman said. "Maybe that's why hockey is the ultimate team sport."

Bettman said NHL officials and all the personnel who come into contact with the players are vaccinated.

"It's something we take seriously," Bettman said. "Health and safety has been and will continue to be paramount."

There are still COVID-19 cases involving players who are fully vaccinated.

The expansion Seattle Kraken are missing a number of players due to COVID-19 protocols for their first game Tuesday night at Las Vegas, and Colorado Avalanche star Nathan MacKinnon will miss their season opener against the Chicago Blackhawks on Wednesday night due to an infection.

The Associated Press contributed to this report.