Pastrnak made it 3-0 at 16:46 of the second period. Sharks defenseman Marc-Edouard Vlasic tried to stop the forward on a breakaway and tripped him up, and his unbalanced shot still got the puck past Kahkonen and in.
"We've got to be better. We give up two goals that are easily coverable, and then the third one was just really fluky and crazy," Quinn said. "The third goal kind of deflated us."
Duclair cut it to 3-1 at 11:13 of the third period when Tomas Hertl set him up in front of the net.
"I'm just looking for a full 60-minute effort from myself," Duclair said. "It's always nice to see a puck go in the back of the net. Obviously, it was a lucky one, but it was good for confidence. For myself especially, before the road trip, to get one in. Hopefully it's the start of something special."
Notes: Pastrnak has four goals in the first three games, and was also the last Bruins skater to score in his first three games of the season (2016-17). Boston has won 12 straight games against San Jose dating back to Feb. 9, 2017.