Erat will miss his second game since being driven into the boards by Florida Panthers defenseman Erik Gudbranson in the first period of a 4-3 Capitals win Saturday. Ward was hurt when he blocked a Sami Salo slap shot with his left leg in a 4-2 win Sunday against the Tampa Bay Lightning.
Ward and Erat made the trip to Montreal, but coach Adam Oates said each needs more time before returning to the lineup.
"[Ward] is still hurt pretty good from that shot," Oates said. "He came on the trip in case he got better, but he just wasn't feeling good this morning. Marty's just loosening up, but he's not quite ready yet."
Oates said there was no timeline for the return of either player.
Wojtek Wolski will take Erat's spot on Washington's second line after being a healthy scratch for five straight games and 12 of the past 14. Eric Fehr, who played in Erat's spot against the Lightning, moves to the third line to fill Ward's regular spot.
While the Capitals are missing players, the Canadiens will welcome back Rene Bourque into the lineup after a 21-game absence due to a concussion that has kept him out since Feb 21. Bourque had been playing left wing on Montreal's top line, with Tomas Plekanec and Brian Gionta, at the time of his injury. That spot has been taken by Michael Ryder, who was acquired five days after Bourque's last game and has 10 goals and eight assists in 18 games with Montreal.
This also will be Montreal's first game since the loss of top-four defenseman Alexei Emelin to a torn anterior cruciate ligament in his left knee. His spot to the right of Andrei Markov will be filled by Davis Drewiske, acquired from the Los Angeles Kings a day before the NHL Trade Deadline for a 2013 fifth-round draft pick. American Hockey League call-up Nathan Beaulieu, the team's 2011 first-round pick, will take Drewiske's spot on the third pairing, with Francis Bouillon.
Here are the projected lines for the Capitals and Canadiens.
Scratched: Jeff Schultz