Seguin pushed the score to 4-1 with the Stars’ third straight power-play goal at 8:59. He beat Swayman with a wrist shot after being left open with plenty of space on the right side.

Brazeau made it 4-2 at 10:41, finishing off Trent Frederic’s wraparound attempt for his own power-play goal.

“When everyone plays the right way, usually everyone enjoys success and benefits from it,” Bruins captain Brad Marchand said. “We’re kind of sitting around it, and it will come. But we as leaders and older guys have to be better and we have to set the pace and lead by example.”

The Bruins outscored the Stars 10-7 in the third period, but Roope Hintz scored an empty net goal for Dallas at 5:58 for the 5-2 final.

“When you’re trying to hold onto a lead, it’s hard because the other team takes everything they have,” DeSmith said. “Not that we sat back, but we played a little more carefully and calculatedly. So I thought they were a little desperate and they brought it in (the third) period.”

NOTES: DeBoer won his 618th game in the NHL, passing Bruce Boudreau and Jacques Lemaire for sole possession of 21st place on the all-time list. … It was Hintz’s 400th NHL game. … Dallas had gone 2-for-21 on the power play through its first seven games before going 3-for-5 on Thursday. … Marchand has not scored a goal in eight games this season. It is his longest opening season drought since 2010/11, when it took nine games to score.