Patrick Berglund scored the shootout winner in the 11th round and the Blues beat the Senators 4-3 on Tuesday night.
The Blues are tied with the Chicago Blackhawks and the Dallas Stars with 83 points in the Central.
Trailing 3-0, the Senators scored three unanswered goals to force overtime, including a goal by Jean-Gabriel Pageau with less than a second left in the third period.
Ottawa goaltender Craig Anderson made 28 saves on 31 shots before leaving the game at the 13:41 mark of the second period.
Andrew Hammond stopped 17 shots in relief of Anderson and made a number of huge saves to keep the Senators in the game. It was Hammond's first appearance since Feb. 11.
Ryan Dzingel also scored for Ottawa.
Jaden Schwartz, with a goal and two assists, led the Blues, while Dmitrij Jaskin and Vladimir Tarasenko also scored. Jake Allen stopped 40 shots.
The Blues are without G Brian Elliott (lower body), Steve Ott (hamstring), Alexander Steen (upper body) and Jori Lehtera (upper body). D Robert Bortuzzo was a healthy scratch.