BOSTON — Toronto Maple Leafs head coach Mike Babcock says he's never seen a line score 20 points in two games.

Until his team's six-period horror show at TD Garden, that is.

David Pastrnak had a hat trick to go along with three assists, linemates Brad Marchand and Patrice Bergeron set up four goals apiece, and the Boston Bruins thumped Toronto 7-3 on Saturday to take a 2-0 lead in their best-of-seven first-round playoff series.

The Bruins' top line of Pastrnak, Marchand and Bergeron combined for six points in a 5-1 victory in Game 1, and added an eye-popping 14 more in this one against the floundering Leafs.

Asked to recall a similar performance, Babcock couldn't.

"No, and if I had, I'd try to block it out of my mind probably," he said. "Obviously they're dominating us."

The same question about a trio registering five goals and 15 assists in two games was put to Leafs defenceman Morgan Rielly, whose answer was more brief: "I just did, yeah."

Toronto's No. 1 line centred by Auston Matthews, which has gone up against the Pastrnak-Marchand-Bergeron unit most of the time at even strength, has been held off the scoreboard through 120 minutes in the series.

Asked about the disparity, the second-year star was blunt in his reply.

"(Expletive) happens, I guess," Matthews said. "It's hockey, we've got to rebound."

Jake DeBrusk, Kevan Miller, Rick Nash and David Krejci had the other goals for Boston. Torey Krug added three assists for the Bruins, who got 30 stops from Tuukka Rask.

Mitch Marner, with a goal and an assist, Tyler Bozak and James van Riemsdyk replied for the Leafs. Frederik Andersen allowed three goals on five shots before getting pulled in favour of Curtis McElhinney, who made 19 saves in relief.

The Eastern Conference quarterfinal now switches to Air Canada Centre for Games 3 and 4 on Monday and Thursday.

"We've got plenty of stuff to look at (and) get ourselves prepped," Toronto defenceman Ron Hainsey said. "We can be better in certainly just about all aspects."

Pastrnak and Marchand were on the ice for all seven of Boston's goals Saturday, while Bergeron was on for six.

Pastrnak (21 years, 324 days) is the youngest player in NHL history to score six points in a playoff game, eclipsing the mark set by Wayne Gretzky (22 years, 81 days) in Game 3 of the 1983 division final.

He also matched a Bruins record for the most points collected through two games of a series, equalling the nine Phil Esposito scored in the 1969 Stanley Cup final.

"Hell of night," Marchand said of Pastrnak's performance. "He's an awesome player."

The Leafs actually had a better start than Thursday when they were nearly run out of the rink in the game's first 10 minutes, but the Bruins grabbed the lead at 5:26 when Pastrnak picked up the puck in front of Andersen and made a slick move to score his second goal of the series.

A Boston power play that went 3 for 6 in the opener then went to work after Toronto was penalized for too many men on the ice, with DeBrusk outmuscling Leafs defenceman Nikita Zaitev, who would be on for all four first-period goals, in front to redirect Krug's feed past Andersen at 9:46.

The goal came moments after Toronto's Kasperi Kapanen rang a shot off the post on a shorthanded breakaway.

Boston's deluge continued at 12:13 when Miller was allowed way too much time and space in the corner before firing a puck in front that deflected in off Zaitsev.

That was it for Andersen, but the Bruins kept coming and went back on the man advantage when Hainsey jumped Tim Schaller after he hit Marner.

Nash buried a rebound on McElhinney just 11 seconds later at the 15-minute mark to make it 4-0 — the 11th power-play goal Toronto has given up in its last seven games.

"It would be hard to pick one (thing), to be honest," Hainsey said of what's ailing the penalty kill.

Already minus the suspended Nazem Kadri and looking for any kind of spark, Babcock put his lines in a blender to start the second, and it paid off when Marner took a nice feed from Zach Hyman at 1:22 to make it 4-1.

But the Bruins got that one back when Hainsey's pass through the neutral zone was intercepted by Krejci, who eventually went to the net to tip home Pastrnak's shot — just Boston's 10th of the game at that point — at 3:46 to stretch the lead to 5-1.

Toronto cut the deficit back down to three at 9:02 when Bozak scored following some good work from Connor Brown.

Pastrnak added his second of the night with 7:26 remaining in the third when he was allowed to walk out from behind the net untouched after Marchand lost the handle on a breakaway.

Van Riemsdyk scored for Toronto on the power play at 14:53, but Pastrnak sealed his hat trick at 18:24 to put an exclamation mark on the beating.

"We gotta go home and get regrouped," Babcock said. "That's our first priority."

Notes: Kadri was suspended three games by the NHL for his retaliatory hit on Boston forward Tommy Wingels in the third period of Game 1. Wingels took part in Saturday's morning skate, but didn't play. ... Leafs winger Leo Komarov appeared to hurt his left knee in a collision with Miller in the second period and did not return. ... Game 5, if necessary, is set for next Saturday in Boston.

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