The Sabres lead the series 3-1. Game 5 will be at KeyBank Center in Buffalo on Tuesday (7:30 p.m. ET; HBO MAX, truTV, TNT, NESN, MSG-B, SNP, SNO, SNE, TVAS).
Josh Doan, Alex Tuch, Peyton Krebs and Bowen Byram each had a goal and assist, and Alex Lyon made 23 saves for the Sabres, the No. 1 seed in the Atlantic Division.
Sean Kuraly scored, and Jeremy Swayman allowed six goals on 29 shots before he was pulled in the third period for Joonas Korpisalo, who stopped all six shots he faced for the Bruins, the first wild card from the East. Viktor Arvidsson exited the game late in the first period with an upper-body injury and did not return.
Buffalo scored three goals in a 4:58 span in the first period for the early advantage.
Krebs gave the Sabres a 1-0 lead at 4:17. Boston failed to clear the puck on the breakout, allowing Buffalo to quickly create a 3-on-1. Tuch controlled the puck in the right circle and fed Krebs, who beat a sprawling Swayman high blocker with a quick wrist shot from the slot.
Doan extended it to 2-0 at 7:10, positioning himself in front of Swayman and redirecting a centering pass from Ryan McLeod.
Zach Benson pushed it to 3-0 at 9:15, poke-checking the puck free on a Boston breakout attempt and scoring five-hole.
Bruins coach Marco Sturm then called a timeout to no avail.
Byram made it 4-0 at 14:24 with his third goal in as many games when he beat Swayman stick side with a shot from the left circle.
Boston managed only five shots in the opening period.
Beck Malenstyn extended it to 5-0 at 5:08 of the third period before Tuch made it 6-0 at 6:32.
Kuraly scored a short-handed goal for the 6-1 final.
