Senators goalie Robin Lehner made 27 saves in the win. Blues goalie Brian Elliott made 16 saves on 16 shots before leaving with a lower body injury, and he was relieved by Jake Allen, who made 15 saves on 17 shots.
“This is a real momentum builder for us,” Sens head coach Paul MacLean said.
Ian Cole and Erik Condra scored their first goals of the season for St. Louis and Ottawa, respectively, and Alexander Steen scored a Blues power play goal in the second period.
Late in the second period, the puck remained loose in the crease after a Chris Neil shot, and as players from both teams converged, the Senators eventually forced the puck across the goal line.
The play was reviewed, and the initial no goal call on the ice stood due to incidental goaltender interference.
That incidental interference also knocked Elliott out of the game. He was slow to get up with the traffic around the net, and after a brief stoppage, Allen entered the game as Elliott skated to the locker room.
Asked about his goalie after the game, Blues coach Ken Hitchcock did not sound optimistic, saying, “We’ll see how long he’s out for.”
Allen was not tested with a shot on goal that period, but Ottawa turned the pressure up in the final period. With a little more than 12 minutes remaining, Eric Gryba’s wrist shot from the blue line was deflected past Allen by Condra positioned in front of the net.
At the 19:19 mark, Ottawa’s luck in crease scrambles changed. Allen did not cover the puck, and Chiasson put it in the back of the net to tie the game with seconds remaining for his sixth goal of the season.
The game went to a shootout after both goaltenders made tough saves in end-to- end overtime action.
The Blues thought they took a first period 1-0 lead on the power play courtesy of Jaden Schwartz, but the official signaled no goal because Jori Lehtera made contact with Lehner.
On the other side of the ice, Condra followed up a short-handed shot against Elliott and jammed the loose puck through, but this goal was also denied. This time, the official blew the whistle before the goal because he lost sight of the puck underneath Elliott.
With less than six minutes remaining in the first, Cole scored his first goal of the season when he fired a rolling puck toward the goal. It knuckled high in the air and got past Lehner for the 1-0 lead.
In a 4-on-3 situation in the second period, the Blues extended their lead. Ottawa’s defense did not pick up Steen trailing the play, and Paul Stastny connected with him on a cross-ice pass. Steen’s wrist shot beat Lehner’s glove for his fifth goal of the year.