Semyon Varlamov made 39 saves in his first start since Game 3 of the first round, a 5-4 loss to the Pittsburgh Penguins on May 20. Ilya Sorokin started the previous four games, including a 5-2 loss to the Bruins in Game 1 on Saturday.
Varlamov, who went 5-1-0 against Boston during the regular season, extended the game when he made a save on Taylor Hall's rebound chance at 13:06 of overtime.
"It was a pretty easy decision," Islanders coach Barry Trotz said. "We have two really good goaltenders. … [Varlamov's] a veteran, he's not scared of these moments and he's been a rock for us all year."
Patrice Bergeron and Brad Marchand scored in the third period for the Bruins, the No. 3 seed. Tuukka Rask made 35 saves.
"[Stuff] happens," Marchand said of Lauzon's turnover. "He's a great player for us. He competes very hard and he's out there every night working his butt off and competing for the group. We all make mistakes, we've all been there. It's tough when it happens to you, but we're going to bounce back. It's not the end of the world, it's 1-1 and we've just to work with that next one.
"It's all about how we regroup in here and move forward. That's the thing about playoffs, you've got to kind of be like an elephant and have a quick memory and just worry about the next day."
Bergeron cut it to 3-2 at 10:34 of the third period with a one-timer between the top of the circles.
Marchand tied it 3-3 with 4:54 remaining from the left circle on a power play after the Islanders were penalized for having too many men on the ice.
"Third period was better where we went low-to-high, getting that part of our offense activated and involved," Boston coach Bruce Cassidy said. "We did a better job, but not good enough early on, and obviously at the end it cost us."
