Backstrom suffered the injury in Game 5 against the Pittsburgh Penguins and also missed the series-clinching Game 6. In 11 playoff games, he has three goals and 13 points.
Forwards Andre Burakovsky and Tom Wilson will both return to the lineup.
Burakovsky was injured in Game 2 of the Capitals opening round series against the Columbus Blue Jackets and hasn’t played since. Wilson missed the last three games of the Penguins series while serving a suspension for an illegal check to the head of Zach Aston-Reese.