Luke Richardson coached the Canadiens in Game 3, assisted by Alexandre Burrows and director of goaltending Sean Burke.
"We didn't have too much time to think about it," Richardson said. "We were running things the way Dom runs it here and it's business as usual."
Ducharme talked to the team on Zoom before and after the game, which the Canadiens won on goals by Josh Anderson with 1:55 left in the third period and 12:53 into overtime.
"I think this morning, there was uncertainty because we didn't know if it was a false positive or what the circumstances were," Montreal captain Shea Weber said after the game. "And then obviously we got to the rink and we found out. I think we're comfortable. Obviously, it hurts to lose Dom. He's been great for us. I think we're comfortable with Luke and [Alexandre]."
Ducharme was "involved with anything that might happen related to the game plan" and will be involved in the preparations for Game 4 on Sunday, Montreal general manager Marc Bergevin said.
"I've talked to Dom twice today," Bergevin said before the game. "He's doing fine. He's at home. It's hard to tell how long he'll be out. We are dealing with Health Quebec and NHL protocols."
According to those protocols, Ducharme must isolate from the team and it is unknown when he can return. The best-of-7 series could continue to June 26 for Game 7, if necessary.
The game at Bell Centre was the first time a United States-based NHL team played in Montreal in 15 months because of concerns related to the pandemic.
"We were clear and transparent with the situation, and the NHL and Health Quebec are comfortable with the game going ahead as scheduled tonight," Bergevin said. "We didn't ask for anything, we were really clear and transparent with the situation."
Ducharme is partially vaccinated, with his second shot administered less than two weeks ago (June 9).
Montreal had four regular-season games postponed from March 22-28 when forwards Joel Armia and Jesperi Kotkaniemi were placed in protocol. The NHL postponed 53 games because of COVID-19 protocol during the regular season, which began Jan. 13. No Stanley Cup Playoff games have been postponed.
The Canada government on June 6 allowed cross-border travel for the final two rounds of the playoffs. The border had been closed to nonessential travel since March 19, 2020.
This is the second consecutive postseason Montreal has been without its coach. Claude Julien was hospitalized because of chest pains during the Eastern Conference First Round in the hub city of Toronto last August. He had a heart procedure and left the playoffs before Montreal was eliminated in Game 6.
This postseason, Colorado Avalanche coach Jared Bednar was cleared for Game 6 of the second round against Vegas after an irregular COVID-19 test result caused him to miss that morning skate.
The Canadiens were 15-16-7 under Ducharme after Julien was fired Feb. 24. Montreal (24-21-11) was the No. 4 seed in the Scotia North Division, won the final three games in the best-of-7 Stanley Cup First Round to eliminate the No. 1 seed Toronto Maple Leafs, and swept the No. 2 seed Winnipeg Jets in the second round. Montreal has won the past two against Vegas after losing Game 1.
The seven-game winning streak was their longest in the Stanley Cup Playoffs since 1993, when they won 11 straight winning their most recent Cup championship. Montreal is in the third round for the first time since the 2014 Eastern Conference Final, a six-game loss to the New York Rangers.
NHL.com staff writer Mike Zeisberger contributed to this report
