After each team scored twice during the first three rounds of the tiebreaker, Tuukka Rask made a toe save on a spin-around attempt by the Senators' Kaspars Daugavins to open the fourth round.
Krejci then followed with a high forehand shot over the glove of Robin Lehner, enabling the Bruins to continue their road dominance of Ottawa and notch their third straight win overall.
Lehner turned aside 33 shots.
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