Colin Blackwell gave the Maple Leafs a 1-0 lead at 5:09 of the first period, redirecting a pass from Jason Spezza at the crease after a Bruins turnover. It was his first goal in four games with Toronto since being acquired in a trade with the Seattle Kraken on March 20.
"The first couple games I've just been kind of getting comfortable. I thought I kind of had a little bit more to give," Blackwell said. "I thought our guys did a really good job of kind of weathering their storm and, you know, playing on our toes all night. It was fun. … It felt like a playoff game."
Pastrnak tied it 1-1 on the power play 50 seconds later with a one-timer that deflected off the stick of Toronto defenseman TJ Brodie.
Rielly gave Toronto a 2-1 lead at 9:43 during a 4-on-4, scoring after William Nylander's wide shot.
"I don't think it was an easy game at all," Rielly said. "I thought they came out well, and we matched. Then it just kind of goes from there. Early on I didn't think our power play was on. They get one on their power play. So, the game's up for grabs. I thought we played well."
Alex Kerfoot made it 3-1 on a breakaway at 18:44.
Marner extended the lead to 4-1 at 8:28 of the second period on a 2-on-1 with Matthews.
Matthews made it 5-1 on the power play at 16:00 on a rebound to the right of the crease. He leads the NHL in goals.
David Kampf extended it to 6-1 47 seconds later.
Jake DeBrusk got Boston within 6-2 at 18:19, redirecting Charlie McAvoy's shot from the point.
"I think we showed good fight in the third," McAvoy said. "We crawled back and had a couple chances at the end. That's a good sign of our makeup and resilience, but we can't go down as much as we did and expect to win."