"I didn't think we looked mentally fresh," Sharks coach Bob Boughner said. "We've played a lot of hockey. We showed battle, but when you're chasing the game, it's tough to show structure. The Bruins are a heavy team. We got better as the game went on, but we were chasing today."
Brad Marchand, David Pastrnak and Derek Forbort each had a goal and an assist, and Patrice Bergeron had two assists for the Bruins (3-1-0). Linus Ullmark made 23 saves.
Jasper Weatherby, Tomas Hertl and Timo Meier scored for the Sharks (4-1-0). Adin Hill allowed four goals on 14 shots before being replaced in the second period by James Reimer, who made 20 saves.
"It was a tough game, probably the toughest so far this season," Hertl said. "Next time we just have to get on them. We gave up too many freebies. … We can play against anybody if we play the right way."
Marchand scored his fourth goal of the season 28 seconds into the first to give Boston a 1-0 lead. Pastrnak passed behind the net to Bergeron, who found Marchand in the slot for a wrist shot past the glove of Hill.
"I thought our start was excellent," Bruins coach Bruce Cassidy said. "You always want to get in front at home, especially that way, playing the right way."