Beagle will undergo surgery for an upper-body injury and be out for an extended stretch. He appeared to get hurt during the second period and did not return.
John Carlson missed his second straight game with an upper-body injury after playing a in 412 in a row, the second-longest run in Washington franchise history (behind Bob Carpenter's 422). Coach Barry Trotz said Carlson will sit Thursday night against the Carolina Hurricanes and that the team will "see after that."
Backstrom saw his last action late in the second. Trotz said Backstrom will travel with the team and could play at Carolina, but did not disclose his injury.
"We are pretty relentless as a team," Washington goalie Braden Holtby said. "(Obviously, the injuries) makes it tougher. Those guys play a huge role on our team but we are just going to have to find different ways to win if they are out. "
Despite the injuries, Washington has won nine straight and leads the NHL with 58 points.
The Associated Press contributed to this report.