Toronto’s Alexander Kerfoot pokes the puck past Bruins goaltender Jeremy Swayman in the first period Tuesday night in Boston. Charles Krupa/Associated Press

BOSTON — Auston Matthews scored his league-leading 49th goal and had an assist as the Toronto Maple Leafs ended Boston’s four-game winning streak with a 6-4 victory on Tuesday night.

Matthews’ goal late in the second period was the fourth of five straight scored by the Maple Leafs, who held a 6-1 lead and flustered the Bruins into a string of retaliatory hits and penalties.

Colin Blackwell scored his first goal since joining Toronto in a trade at the deadline. Morgan Rielly, Alexander Kerfoot and Mitchell Marner each had a goal and an assist.

John Tavares added two assists and Erik Kallgren had 23 saves after entering in the first period, replacing Petr Mrazek, who left with an undisclosed injury. The Leafs also lost a pair of defensemen to injuries, but had more than enough offense before the Bruins cut the margin.

David Pastrnak scored his 38th goal for Boston. Jake DeBrusk, Curtis Lazar, Taylor Hall also scored for the Bruins, who could not keep up with the speedy Maple Leafs.

Jeremy Swayman allowed six goals on 25 shots before being replaced by Linus Ullmark at the start of the third period.

The game was close early as Blackwell and Pastrnak scored less than a minute apart. But the 1-1 tie lasted only a few minutes before Rielly scored and the Leafs broke open the game and won for the third time in four games since the trade deadline.

Kerfoot scored on a breakaway with 1:16 left in the first period, and the Leafs added three more goals in the second before DeBrusk’s goal cut the lead to 6-2 late in the period.

The Bruins’ frustrations had already boiled over, adding to the Leafs’ lead after Taylor Hall knocked Toronto defenseman Lya Lyubushkin out of the game with a punch, retaliating for what Hall felt was a hit from behind.

The roughing penalty led to Matthews’ goal with four minutes left in the second and David Kampf struck again for the Leafs just 47 seconds later. Kerfoot picked up an assist on the goal and was leveled by Connor Clifton well after the play as he skated to celebrate with his teammates.

The Bruins did make it interesting when Hall scored with 2:22 remaining on a goal that was initially disallowed until replays confirmed the puck got through Kallgren’s pads.

NOTES: Boston’s Brad Marchand received a 10-minute misconduct penalty after the second period.