Montreal Canadiens coach Claude Julien was admitted to a Toronto hospital after experiencing chest pains following his team's game on Wednesday night.
Montreal GM Marc Bergevin said he does not believe the issue is related to COVID-19, but Julien was undergoing tests on Thursday.
"He's for sure in really good hands," Bergevin said Thursday. "I spoke with him this morning and we're hoping for the best for him right now."
Kirk Muller will assume head-coaching duties for the rest of the Philadelphia series. Montreal lost 2-1 to the Flyers in Game 1 of their quarterfinal series on Wednesday. Game 2 is Friday.
Julien, 60, is in his second stint coaching the Canadiens. He led the Boston Bruins to a Stanley Cup in 2011.
Canadiens captain Shea Weber said Bergevin told him at practice about Julien being hospitalized. The news trickled through the team and then Bergevin held a team meeting.
The 12th-seeded Canadiens were the final team included in the NHL's expanded 24-team tournament, but pulled off an upset of the Pittsburgh Penguins in the qualifying round.
Bergevin said the team was still figuring out protocol for Julien possibly rejoining the Canadiens in the bubble.
"No decision has been made yet," Bergevin said. "Possible Claude will come back to hotel, more likely he returns home. We don't have the details yet."