TORONTO — With a chance to grab a stranglehold of this first-round series against the Toronto Maple Leafs, the Bruins played their best game of the playoffs Saturday night.

Going away from their goalie rotation and starting Jeremy Swayman for the second straight game, the B’s did a tremendous job of limiting the Leafs’ scoring chances and grinded out a 3-1 victory at Scotiabank Arena.

The B’s now have a 3-1 series lead – a position they know all too well from last season in their seven-game series loss to the Florida Panthers – as they head back to Boston to try and close it out on Tuesday in Game 5 at the Garden.

James van Riemsdyk, Brad Marchand and David Pastrnak scored for the B’s and Swayman made 25 saves for the win.

William Nylander had missed the first three games of the season, reportedly for an issue with migraines, but the 40-goal scorer made his first appearance on Saturday night.

And the B’s tempted fate by giving the Leafs the first power play of the game early when they took a too many men penalty just 3:42 in, but Toronto could not cash in, nor could they capitalize on a 4-on-3 power play later in the period. With Pat Maroon and Joel Edmundson in the box with matching roughing penalties, Charlie McAvoy was called for slashing veteran defenseman T.J. Brodie, making his first appearance in the series as well, giving the Leafs a 4-on-3 for 53 seconds. They did nothing with it.

The B’s also squandered their first power play chance in the first when Mitch Marner tripped McAvoy.

But the B’s created their first big break of the game. Mason Lohrei made a good decision to step up on a loose puck along the left wall in the Toronto zone, beating Ryan Reaves to it and getting it to van Riemsdyk at the inside of the left circle. With all sorts of time and space, the former Leaf made a move to his backhand and slipped it through Ilya Samsonov’s pads at 15:09 for the 1-0 lead. It was van Riemsdyk’s first goal since Feb. 17. It was Lohrei’s first career playoff point.

The B’s took a 2-0 lead at 8:20 of the second period after they took another bad penalty. With multiple players battling for a puck in the right corner of the Leafs’ zone, Max Domi hit Pastrnak with an obvious crosscheck.

On the ensuing power play, McAvoy had the puck in the high slot and Samsonov came out to the top of the crease. McAvoy simply moved the puck to Marchand on the right side and the captain one-timed it into the wide open net.

Then, with 42 seconds left in the period, the B’s appeared to stick the dagger into the Leafs’ collective heart. Pavel Zacha took a big hit from Jake McCabe to deflect Hampus Lindholm’s pass ahead into the Toronto zone. That’s where Marchand just beat Brodie to the puck to chip it ahead and create a quick 2-on-0 with Pastrnak. Marchand dished it to him and Pastrnak buried it past Samsonov.

As the clock wound down to end the period, the Leafs fans lustily booed their team off the ice.

But the Leafs, who switched out Samsonov for Joseph Woll and would come back on the ice for the third period without their best player, Auston Matthews, got on the board quickly at 5:43. Mitch Marner, who’d been very quiet this series, was able to beat Swayman with a sliding backhander.

The Leafs stormed the B’s zone after that but they killed some of their own momentum when Nylander took an offensive zone penlty at 10:48.

The B’s could not stretch the lead and then, with 5:43 remaining in the third, Pastrnak was called for slashing. As they’ve done almost the entire series, the B’s did a great job of killing it.