It is the third consecutive season the two teams are facing each other in the playoffs and the fourth time in five years. The Rangers eliminated the Capitals in seven games in the second round last season.
Game 2 is today in Washington.
Ottawa’s Craig Anderson made 48 saves in a spectacular goaltending performance, helping the Senators to a 4-2 win over the Montreal Canadiens.
Jakob Silfverberg and Marc Methot scored early in the third period for the Senators to give the hosts the lead, while Erik Karlsson and Guillaume Latendresse also scored.
Ottawa were outshot 50-31, but saw Anderson easily win the goaltending duel with Carey Price, who was beaten twice through the pads.
Rene Bourque and Brendan Gallagher scored for Montreal, who set a team record for shots in a regulation-time playoff game.
Montreal center Lars Eller was felled in an open-ice hit by Senators defenseman Eric Gryba. He was wheeled off on a stretcher bleeding heavily from the nose, and was taken to a hospital with what the team said were head and facial injuries.