With the victory, the Senators ended the Bruins' 11-game winning streak in Ottawa. It had been so long since the Senators beat the Bruins at home that only Spezza, Chris Neil and Chris Phillips remain on the roster from that previous victory.
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After a rough start, things turned around for the Senators with a solid third-period effort that was led by their captain.
Spezza tied the game 2-all early in the third, scoring from the side of the net off a pass from Erik Karlsson at the point. It was Spezza's first goal in five games.
"It's been a few games for me and it was an important game," Spezza said. "We were using this game as a bit of a measuring stick, and it was a big goal."
Rask said he felt the Bruins started off strong but had a few lapses throughout.
"It's one of those days when you're not on top of your game, you don't even know he's there, and I didn't know (Spezza) was there," Rask said. "I stretched myself there, but I couldn't get my pad on it and it's a goal."
The goal seemed to energize the Senators. Anderson then made a great save on Carl Soderberg. Soderberg had a second chance and kept shoving at the puck until it crossed the line, but upon review, it was clear the whistle had blown.
"It was a good rebound game for everybody," Anderson said. "We've got something we can build off of now."
The Senators took their first lead of the game at 5:42 of the third on Cowen's third of the season as he beat Rask through the legs.
Ryan's goal at the halfway mark of the period sealed the victory as he took the puck from Reilly Smith and beat Rask through the legs to give Ottawa a 4-2 lead.
Ryan had to leave the game with just more than three minutes remaining after taking an elbow to the head by Dennis Seidenberg. There was no penalty on the play.
MacLean said he was given no explanation by the officials and that he believed the play is worthy of being reviewed.
"All the ones that you see around the league in the first 20 games, it certainly seems that one could be reviewed as well," the Senators' coach said.
Ryan will be evaluated Saturday. MacLean had no further updates on the winger's status following the game.
Seidenberg felt for Ryan and said there was no intent to injure him.
"The puck is loose, I'm going for the puck and I'm turning into the puck and I think he's reaching," Seidenberg said. "I would never go after a guy's head and I hope he's fine so that's all I can say."
Ottawa had a poor start to the first period, giving up two goals and being outshot 13-6.
Eriksson opened the scoring at 6:03 of the first as he tipped Matt Bartkowski's shot. Just more than three minutes later, the Bruins made it 2-0 as Marchand made his way between Zack Smith and Colin Greening and beat Anderson with a great wrist shot.
The Senators salvaged the period at 19:10 as Neil scored his third of the season and beat Rask to the top left corner to make it 2-1.
"Any time you score late in the period, it's a big momentum swing for you if you can take advantage of it," MacLean said. "I felt we were getting stronger and better as the game went along."