Josh Anderson scored into an empty net for his second goal of the game with 1:44 remaining to push it to 5-3, and Gallagher then scored the Canadiens’ second empty-net goal with 59 seconds left for the 6-3 final. Gallagher also had two assists.
“We were fine,” Anderson said. “We were confident in our abilities to come back and just really stick to our game. We were doing everything we can to produce and try to win that game, and we wanted to keep pressing and that’s what we did.”
Christian Dvorak had a goal and three assists, and Jake Evans had two assists for Montreal (33-27-7), which moved into the second wild card into the Stanley Cup Playoffs from the Eastern Conference, one point ahead of the New York Rangers. New York lost 2-1 to the Calgary Flames at home on Tuesday.
Sam Montembeault made 22 saves and improved to 7-0-1 in his past eight starts.
Travis Hamonic had a goal and an assist, Drake Batherson and Michael Amadio scored, and Linus Ullmark made 27 saves for Ottawa (36-26-5), which had points in eight straight games (7-0-1).
“We knew we weren’t going to win every game for the rest of the year,” Batherson said. “We’ve just got to put it behind us.”
The Senators lead the Canadiens by four points for the first wild card from the East.
“We’ll learn from the mistakes and do some video and regroup,” Hamonic said. “There’s no sense beating ourselves up over it. It wasn’t a great effort but we’ll be ready to go.”
Dvorak gave Montreal a 1-0 lead at 2:07 of the first period. He scored for a second straight game, taking a pass from Gallagher on a breakaway and deking around Ullmark, who had lost his stick 36 seconds earlier while making a save on Patrik Laine.
Batherson tied it 1-1 at 16:42 when he carried the puck up the middle and sent a wrist shot past Montembeault’s glove from the top of the slot.
“I was kind of waiting for one of the ‘D’ to come at me to dish it out,” Batherson said. “And they gave me the lane, and I took a shot and luckily it went in.”