Backstrom, who sat out Wednesday’s game against Philadelphia with an illness, glided in to the Bruins’ zone and ripped a left-circle wrister past Jaroslav Halak for the go-ahead goal with 14:14 remaining.
The TD Garden crowd gasped, but play continued and there was no immediate on-ice retaliation.
The Bruins captain tumbled back onto the ice quickly and rejoined the play.
Jakub Vrana also had a goal for the Capitals, whose streak against the Bruins dates to March 29, 2014.
Braden Holtby made 39 saves, improving to 12-0-0 against Boston during the Capitals’ streak, and 16-2 in his career against the Bruins.
Halak had 18 saves for Boston, which had its five-game win streak snapped.
Washington led 1-0 after the first period despite being outshot 17-5. T.J. Oshie grabbed a giveaway by the Bruins and flipped the puck from the Capitals’ end to a wide-open Vrana, who beat Halak with 13:22 to play.
Tensions boiled over in the second when Washington’s Lars Eller and Boston’s Brad Marchand got tangled up during a play. Eller, whose celebration in front of the Boston bench after scoring the Capitals’ seventh goal in the opener drew postgame criticism from Marchand, was sent to the penalty box for unsportsmanlike conduct.
Donato tied it at 1 with 5:49 to play in the second. But, Ovechkin quieted the TD Garden crowd 39 seconds later when he converted after a feed from behind the net to make it 2-1.
Krejci ripped the tying power-play goal past Holtby from the right circle with 15:23 remaining in the third.
Ovechkin scored into an empty net with 1:35 left to seal the victory.
NOTES: Bruins D Charlie McAvoy missed his seventh straight game with a foot infection. He participated fully in Wednesday’s practice and could return for Saturday’s game against Toronto. … Washington D John Carlson, born in nearby Natick, Massachusetts, celebrated his 29th birthday. … Boston announced a partnership with the Boston Pride of the National Women’s Hockey League team on Thursday. The Bruins are the fourth NHL franchise to partner with a NWHL team.
Capitals: Host Columbus on Saturday night.
Bruins: Visit the Maple Leafs on Saturday night.
Source: Fox Sports