BOSTON — Jake DeBrusk had two goals and an assist for the Boston Bruins in a 5-1 win against the Toronto Maple Leafs in Game 1 of the Eastern Conference First Round at TD Garden on Saturday.

Jeremy Swayman made 35 saves for Boston, which is the No. 2 seed from the Atlantic Division. Brad Marchand and Charlie McAvoy each had two assists.

“I really liked our team discipline,” Bruins coach Jim Montgomery said. “I liked our execution. I liked the emotion we played with. And I thought the physicality of our group was very evident.”

David Kampf scored, and Ilya Samsonov made 19 saves for Toronto, which is the No. 3 seed from the Atlantic. Forward William Nylander missed the game with an undisclosed injury.

“I thought it started out a pretty good game,” Maple Leafs forward Auston Matthews said. “And then just little mistakes, and they’re a very patient team. And obviously [they] executed on the mistakes that we made, so it’s a game of inches. We get a taste of what the series is all about here in this game.”

Game 2 of the best-of-7 series will be in Boston on Monday.

John Beecher, who was playing in his first NHL playoff game, gave the Bruins a 1-0 lead at 2:26 of the first period, finishing off a 2-on-1 rush with Jesper Boqvist.

“I knew the energy was going to be there in the building,” Beecher said. “We came up for the national anthem and [I] honestly got chills just sitting on the bench and hearing the crowd and how fired up everybody was to be there.”

Brandon Carlo made it 2-0 at 5:47 of the second period with a one-timer off a pass from DeBrusk from below the goal line.

The goal came just over a minute after Matthews beat Swayman, who came out of his crease, to a loose puck but hit the post on his attempt at an open net.

“Outside of those mistakes, the flow of the game and everything, we’re right there,” Maple Leafs coach Sheldon Keefe said. “We have our chances and we don’t make good on them. But just too many mistakes, little mistakes like that 2-on-1, the penalties, careless with our stick. That kind of stuff is not good enough.”

DeBrusk then extended it to 3-0 at 15:02, beating Samsonov with a wrist shot from above the right face-off circle on the power play.

“I just wanted to play a fast, hard forechecking style,” DeBrusk said. “I didn’t put numbers or anything on it. Obviously, I think the biggest thing that we talk about, even in the room, is we stay in the moment, so I didn’t actually set any goals. I just wanted to help the team any way I can.”

DeBrusk scored on the power play again at 17:34, knocking in Marchand’s pass at the top of the crease to push it to 4-0.

“It’s obviously a very skilled team over there,” Toronto forward Mitch Marner said. “When you give them a lot of power plays, they’re going to start feeling really good about their game.”

Kampf cut the lead to 4-1 at 1:39 of the third period. Connor Dewar retrieved a rebound and sent a backhand feed to Kampf for a one-timer in the slot.

Trent Frederic scored an empty-net goal at 17:52 for the 5-1 final.

“I think we stuck to the game plan really well,” Swayman said. “It starts with our coaching staff giving us one to be effective against this team. They’re obviously a great team and they forecheck well, and I think that our game plan was excellent.”

NOTES: Marchand passed Patrice Bergeron and David Krejci for second in Boston’s history in playoff points. He has 130 points (53 goals, 77 assists) in 147 games, trailing only Ray Bourque (161 points; 36 goals, 125 assists in 180 games). … The Bruins have a 38-20 series record all-time when taking a 1-0 lead in a best-of-7 series, including 29-13 when starting at home.