Christian Dvorak and Nick Suzuki each scored, and Sam Montembeault made 28 saves for Montreal (39-31-9), which had won six straight.
“We’ve got to dial in our starts and start on time,” Canadiens forward Cole Caufield said. “We can’t always come back all the time. It’s not any sort of panic button, but it’s for sure something that we’ve got to look ourselves in the mirror and face head on.”
Montreal could have clinched a playoff spot and moved within a point of Ottawa for the first wild card with a regulation win. The Canadiens hold the second wild card, six points ahead of the Columbus Blue Jackets and New York Rangers.
“It happens, right? Eighty-two games, you’re going to have off nights,” Montreal defenseman Kaiden Guhle said. “But it’s a tough, tough night. I mean, myself, I wasn’t nearly good enough for the team today. I didn’t feel great.”
Pinto gave the Senators a 1-0 lead 28 seconds into the first period when he finished on a centering pass from Greig at the edge of the crease.
“I thought we just got on them quick,” Pinto said of the team’s start. “Got behind them, forechecked their D. I think that’s been our MO all year. We got two quick goals in front of the net and that obviously set us up for a pretty good game.”
Cozens scored on a Nikolas Matinpalo rebound crashing the net to push it to 2-0 at 4:18.
“Can we bend not break in the first period? We haven’t been able to do that,” Canadiens coach Martin St. Louis said. “Fortunately, I felt like we stopped the bleeding at 2-0; I just wanted to get out of that period down 2-0. But some nights, it’s just too big of a hole.”