The Boston Bruins placed forwards Anton Blidh and Trent Frederic and goalie Jeremy Swayman in the NHL’s COVID-19 protocol on Thursday.

With the number of coronavirus cases and game postponements rising across the league, the addition of Blidh, Frederic and Swayman gave the Bruins six players in the protocol. One team staff member also was placed on the list Thursday.

Patrice Bergeron, leading scorer Brad Marchand and fellow forward Craig Smith went on the protocol list earlier this week. Bergeron entered Wednesday, one day after Marchand and Smith. All six players could be out until late December.

Coach Bruce Cassidy, who tested positive Nov. 30, just rejoined the team on Monday.

The Nashville Predators also have been hit hard, announcing Thursday that assistant coach Dan Hinote had been added to the protocol list.

More than 140 NHL players have been on the protocol list this season in a league that has proudly noted that all but one of its approximately 700 players are considered fully vaccinated, even if booster shots are not mandated.

It is a discouraging trend for the league, which plans to allow its players to participate in the Winter Olympics in China in February unless COVID-19 disruptions prove to be too much.