BOSTON -- The Ottawa Senators accomplished all kinds of things Thursday night, and they did it without their best player.

The Sens, who have been hammered by injury, qualified for the playoffs with a tie in regulation and then won the shootout for a 2-1 win over Boston that finished off the franchise's first season sweep of the Bruins in 24 tries.

They also ended Boston's six-game winning streak and moved a point ahead of the Bruins, who clinched a spot Tuesday, into second place in the Atlantic Division, with a game in hand heading into the final weekend.

They also grabbed a three-point lead over the fourth-place Toronto Maple Leafs as the Senators, Bruins and Leafs all battle for the right to not play the Washington Capitals in the first round of the playoffs (the Tampa Bay Lightning and New York Islanders are also hanging on).

And the Senators did all this without leading scorer (and defenseman) Erik Karlsson, forced to sit because of a foot injury, and others.

"You want the calm guy?" asked coach Guy Boucher. "It's a great moment -- I have to be honest here. When you look at what the players have lived through, what the organization had to go through this year, the adversity that the players had to battle through even today -- missing lots of key guys. I can't help but be so proud and impressed by this group."

He went on to credit management and moves that were made to keep this team competitive. The Senators came into Thursday's game 3-4-3 in their last 10 but played their usual tight-checking game and got it done.

"It's hard to play against. It's not fun," said Bruins interim coach Bruce Cassidy, who fell to 18-7-1 since replacing the fired Claude Julien after losing his first overtime game.

Craig Anderson made 28 saves through regulation and overtime and stopped all three in the shootout -- to go to 30-26 all-time in the competition. Kyle Turris beat Tuukka Rask with the only shootout goal, as Rask fell to 21-28 lifetime in shootouts.

The Senators know there is still work to be done, starting with Saturday night's home game against the New York Rangers and Sunday's game at the still-alive Islanders. But this was a step.

"It's awesome," Ottawa's Mark Stone said. "Last year was a terrible feeling. I think when you make the playoffs -- What was it? Two years ago? -- on a Cinderella run, that feeling of accomplishment was incredible. And then the failure from last year. And we bring in a new group this year, a whole new staff, and we bought in from the start."

Boston, playing without the suspended Brad Marchand and losing swift defenseman Torey Krug to a knee injury in the first period, lost all 10 games this season to Ottawa, the Toronto Maple Leafs and Washington Capitals -- its three potential playoff opponents.

The Bruins host Washington in Boston's regular-season finale Saturday.

Anderson, who beat the Bruins in all four meetings this season, stopped David Pastrnak on a breakaway in the second period.

Rask made 25 saves as his personal four-game winning streak ended.

"Both teams played good defense. There wasn't a whole lot of room out there," Rask said. "It was kind of just a battle of defenses, not a whole lot of room."

Drew Stafford scored a power-play goal for Boston in the first period. Alexandre Burrows, picked up at the trade deadline, answered in the second. Both scored off bad clearing passes.

CSNNE reported Krug left TD Garden on crutches, with a "bulky brace" on his right knee. Missing both Krug and Marchand for most of the game and especially in the 3-on-3 OT clearly hurt Boston. Being without Krug, Boston's best offensive and quickest defenseman, long term could be crushing.

Ottawa's Viktor Stalberg left in the third period after Adam McQuaid's hit sent him head-first into the boards. The hit appeared to be clean.

NOTES: Boston LW Brad Marchand talked about his two-game suspension for spearing Tampa Bay's Jake Dotchin on Tuesday. Said Marchand: "It was definitely selfish and undisciplined at the time." Dotchin, who returned to the game, said Thursday he was OK but experiencing some pain, and added that Marchand's stick got him near the eye while he was lying on the ice. ... Bruins RW Frank Vatrano, who missed four games with an upper-body injury, returned. ... Ottawa D Cody Ceci returned after missing two games with an injury. ... Bruins RW David Backes played his 800th NHL game. ... Bruins C Jakob Forsbacka-Karlsson, signed out of Boston University, obtained his work visa and was on the ice for the warmup. He didn't dress for the game. ... Boston RW David Pastrnak won the annual 7th Player Award, voted by the fans for the Bruin who exceeded expectations.