Gambrell gave Ottawa a 1-0 lead at 8:55 of the first period, retrieving a dump-in behind the net and wrapping it around the left post.
"We knew it was going to be a hard task, and I think we came in and pitched a really good game," Senators defenseman Travis Hamonic said. "It's unfortunate we don't get the result, but it was a good, solid effort [throughout] our lineup."
Krejci tied it 1-1 with a 5-on-3 power-play goal at 11:33, putting in the rebound of Lindholm's point shot.
"'[Patrice Bergeron] gave me a good little flash screen, and I knew he's good with his stick," Lindholm said. "If you get a shot from the slot like that, you kind of want to take it, so I end up ripping it in, and great job by 'Bergy' and [Krejci going] in there and crashing the net."
DeBrusk gave the Bruins a 2-1 lead at 15:52. Brad Marchand connected a cross-ice pass between two defenders to DeBrusk, who deked around Sogaard to push the puck through at net front.
"It was one of those passes where it was just all-world, and I was happy to finish it for him," DeBrusk said. "I just didn't even think; it was instinct. The pass comes, the pass has gotta make it there, and once it does, it's a split-second decision, and I just thought I could beat [Sogaard] with my speed."