Following a turnover by Peyton Krebs at the defensive blue line, Pastrnak took a stretch pass from Hampus Lindholm, skated in on a partial breakaway, and made a backhand-to-forehand deke on Alex Lyon before tucking the puck in at the right post.
Elias Lindholm also scored for the Bruins, who are the first wild card from the Eastern Conference. Jeremy Swayman, who was pulled in the third period of a 6-1 loss in Game 4, made 26 saves.
Rasmus Dahlin scored for the Sabres, who are the No. 1 seed from the Metropolitan Division. Lyon made 27 saves.
Dahlin gave Buffalo a 1-0 lead on a power play at 3:35 of the first period. Jason Zucker's initial pass attempt for Tage Thompson was blocked by Bruins defenseman Andrew Peeke, but the puck bounced right back to Zucker, allowing him to then feed Dahlin, who buried a one-timer off the near post from the right circle.
It was the Sabres’ first power-play goal in the month of April, ending an 0-for-39 drought (regular season and playoffs).
Lindholm tied it 1-1 at 9:24 of the second period. Lyon made the save on his initial shot from the right of the net, but the rebound bounced into the high slot, where Lindholm gathered it and spun around for a wrist shot that beat the screened goaltender inside the right post.
Buffalo forward Noah Ostlund left the game midway through the first period with a lower-body injury after getting tangled with Boston forward Casey Mittelstadt.
