Ryan left the game with just over five minutes remaining in the second period after a collision behind the net, but he returned shortly after. However the Senators opted on the side of caution and kept him out of the lineup for the third period.
Montreal opened the scoring as Nygren beat Hammond with a shot from just inside the blue line. Ottawa tied the game minutes later as Conacher passed to a trailing MacArthur.
Ottawa ended the period with a 2-1 lead on Ryan's power-play goal.
The Senators made it 3-1 on Michalek's goal as he managed to dig the puck out during a goal-mouth scramble and roofed it over Budaj.
Conacher made it 4-1 with a power-play goal, while Zibanejad picked up his first of the preseason to make it 5-1.