Giroux said the Flyers aren't winning enough battles, aren't competing hard enough.
"We're just going through the motions."
Coach Peter Laviolette refused to comment on Giroux's remark.
"We have to show a little bit more emotion," said center Danny Briere, who scored the Flyers' lone goal. Briere added he has been on teams that have gone through similar struggles. "And there's only one way out, and it's to keep sticking together, to keep working hard. Maybe we have to want it a little more and things will turn around at some point."
In a battle of backup goalies, Montreal's Peter Budaj outdueled Brian Boucher. Not that the Flyers gave Budaj much work. Their attack was out of sync all night, and their power play was ineffective.
Montreal (9-4-1) took control as Thomas Plekanec scored on his own rebound from the right circle after defenseman Braydon Coburn blocked his original shot. That gave the Canadiens a 3-1 lead with 15 minutes, 28 seconds left in the game.
Rene Bourque later added an empty-net goal.
The Flyers (6-9-1) seemingly got a break when Carey Price, who has been one of the NHL's best goalies in the first month of the season, was scratched because of the flu.
Then again, the Rocky statue probably could have been in goal in the first period and blanked the Flyers, who fired just two shots and rarely had the puck down the other end as they fell into a 1-0 hole.
The Canadiens, one of the NHL's surprise teams, made it 2-0 as David Desharnais scored 1:15 into the second period, beating Boucher from out front as Max Pacioretty collected his second assist of the night.
The Flyers got to within 2-1 as Briere's shot, a knuckleball, appeared to deflect off defenseman Andrei Markov and trickled past Budaj with 6:04 left in the second period. It was just the Flyers' seventh shot of the game.
The Flyers, coming off a 5-3 loss in New Jersey on Friday, squandered four power-play chances in the second period, collecting a total of five shots during that eight-minute span. Whether on the power play or at even strength, they failed to mount any sustained pressure against a goalie who took a 4.33 goals-against average and .866 save percentage into the game.
"The third period we're down 2-1 and have to find a way to get it done," Giroux said. "In New Jersey, we're tied at 3-3 [going into the third], and we didn't get it done."
In their eight road losses, the Flyers have been outscored by 12-3 in the third period.
The Flyers reached the one-third mark of the 48-game season Saturday on pace to miss the playoffs for just the second time in the last 18 seasons.