Daniel Alfredsson also scored for the Senators, who were outshot 39-20.
Milan Lucic scored on the power play about midway through the first period to give the Bruins a 1-0 lead. He converted a pass to the net by linemate Nathan Horton as Boston had a 20-5 advantage on shots in the opening period.
Alfredsson tied the score at 5:09 of the third and Rundblad got the winner while Boston's Rich Peverley was in the penalty box serving 4 minutes for a high sticking double minor.
|PPG - Milan Lucic (1) Wrist shot - ASST: Nathan Horton (1), David Krejci (1)|
1 - 0 BOS
|Daniel Alfredsson (1) Wrist shot - ASST: Colin Greening (1)|
1 - 1 Tie
|PPG - David Rundblad (1) Slapshot - ASST: Sergei Gonchar (1), Jason Spezza (1)|
2 - 1 OTT
|Milan Lucic Kneeing - 2 min against Jared Cowen|
|Zenon Konopka Hooking - 2 min against Brad Marchand|
|David Rundblad Holding - 2 min against Rich Peverley|
|Mika Zibanejad Delaying Game-Puck over glass - 2 min|
|Sergei Gonchar Holding - 2 min against Zdeno Chara|
|Daniel Paille Tripping - 2 min against Bobby Butler|
|David Rundblad Boarding - 2 min against Chris Kelly|
|Nick Foligno Boarding - 2 min against Zdeno Chara|
|Daniel Paille Hooking - 2 min against Daniel Alfredsson|
|Rich Peverley Hi stick - double minor - 4 min against Zack Smith|