Seguin pushed it to 4-1 with another power-play goal at 8:59 after he was left open with plenty of space on the right side to beat Swayman with a wrist shot.
Brazeau cut it to 4-2 at 10:41 on the power play, finishing off Trent Frederic’s wraparound attempt.
“When everybody’s playing the right way, usually everyone enjoys success and benefits from it,” Bruins captain Brad Marchand said. “We’re kind of right around it, and it’s going to come. But us as leaders and older guys, we need to be better and we need to set the tempo for that and kind of lead by example.”
The Bruins outshot the Stars 10-7 in the third period, but Roope Hintz scored an empty-net goal for Dallas at 17:58 for the 5-2 final.
“When you’re trying to hold on to a lead, it’s tough because the other team brings everything they have,” DeSmith said. “Not that we sat back, but playing a little bit more careful and calculated. So I just thought they were a little bit desperate and they brought it in [the third] period.”
NOTES: DeBoer won his 618th game in the NHL, moving into sole possession of 21st place on the all-time list and breaking a tie with Bruce Boudreau and Jacques Lemaire. ... Robertson scored his 137th goal, the second-most by a Stars/Minnesota North Stars player through 300 games, behind Dino Ciccarelli (158). … It was also Hintz's 400th NHL game. ... Dallas had been 2-for-21 on the power play through its first seven games before going 3-for-5 on Thursday. ... The Stars had also gone six games without allowing a power-play goal -- leading the League going into the game at 95.5 percent on the penalty kill -- before allowing Brazeau's goal. ... Pastrnak scored his 78th game-opening goal, the most among all players dating to his debut season in 2014-15. … Marchand has not scored a goal through eight games this season. It’s his longest season-opening goal drought since 2010-11, when it took nine games to score.