Timashov made it 2-0 at 15:44 when he shot past Halak's glove from the slot for his first NHL goal.
"Of course, it's a dream come true, always a dream to score my first goal," Timashov said. "I didn't think it was going to come this soon because I don't score a lot of goals, I'm more of a passer, but I'm happy to score my first one."
DeBrusk cut the lead to 2-1 with 21 seconds left in the first with a one-timer from the slot off a pass from Charlie Coyle from behind the net.
Boston outshot Toronto 15-3 in the second period, when the Maple Leafs were called for four minor penalties, but neither team scored.
"You just have to keep calm a little bit," Rielly said. "It's easy to get worked up when you're on the penalty kill a lot. They had lots of zone time, but I think it was important to keep calm, and I think we came out in the third and played pretty well."
Heinen tied it 2-2 at 1:36 of the third when he shot past a sprawling Andersen from the right face-off dot on the power play.