Artem Zub put Ottawa up 2-1 at 16:53 with a snap shot from in close.
Jake Sanderson made it 3-1 at 5:48 of the second period. The Senators defenseman drove along the goal line from the left side and scored on a backhand inside the far post.
Drake Batherson pushed it to 4-1 at 6:58 when he curled the puck around Montembeault’s pad for Ottawa’s fourth straight goal.
Suzuki cut it to 4-2 at 8:50 with a power-play goal, snapping a shot over Ullmark from low in the left face-off circle.
“There’s definitely some mental mistakes which cost us tonight,” Suzuki said. “When you play man on man you can’t really do that. Guys were worried about their guy, and we let stuff kind of slip around us and get in open spots. So it’s definitely been a concern, but I don’t think we’re going backwards.”
NOTES: Suzuki has nine points (four goals, five assists) on a six-game point streak. … Caufield has 10 points (two goals, eight assists) on an eight-game point streak. … Slafkovsky scored his 50th goal in 225 NHL games with Montreal. The No. 1 pick in the 2022 NHL Draft is the third player in NHL history born and trained in Slovakia to score 50 career goals at age 21 or younger, joining Marian Gaborik (84) and Marian Hossa (62). … Senators forward David Perron, who had an assist on Tkachuk’s goal, was playing in his 1,200th NHL game. … Tkachuk has 410 points, tying Wade Redden for fifth in Senators history. Daniel Alfredsson is Ottawa’s all-time leader with 1,108, followed by Jason Spezza (687), Erik Karlsson (518) and Alexei Yashin (491).