TORONTO -- Mitch Marner and Auston Matthews have played sparingly together at even strength early in their careers.
With injured Toronto captain John Tavares sitting out, the two connected to give the Maple Leafs a big win.
Marner's hard shot after taking a pass from Matthews glanced in off teammate Morgan Rielly at 3:54 of overtime to give Toronto a hard-fought 4-3 win over the Boston Bruins 4-3 on Saturday night.
"I saw (Matthews) go around the back of the net and I didn't want to get too close," said Marner, who finished with two assists. "I knew that if there were sticks in the way he couldn't make the pass so I tried to stay higher in the slot."
The goal was initially credited to Marner, but changed to Rielly — his second of the night — after the game.
"It went in," Matthews said. "That's all that matters."
Alexander Kerfoot and Dmytro Timashov also scored for Toronto. Frederik Andersen stopped 42 shots.
David Pastrnak had a goal and an assist, and Jake DeBrusk and Danton Heinen also scored for the Bruins. Jaroslav Halak finished with 25 saves.
"Give their goaltender credit," DeBrusk said. "He gave them a chance."
The Maple Leafs played their first game without Tavares, who broke a finger Wednesday and will miss at least two weeks.
"It's big," Rielly said of the victory. "A team within the division, not having (Tavares) ... just a point in our year where we want to get going.
"We answered the bell."
Toronto coach Mike Babcock wouldn't reveal his plan moving forward in Tavares' absence — namely whether or not Matthews and Marner will continue playing together.
"We'll just try to evaluate," he said. "We'll look at it, get it figured out and then go from there."
Down 2-1 despite a dominant second period, the Bruins tied the score at 1:36 of the third just as a Maple Leafs penalty was about to expire when Heinen got his first.
Toronto replied just 61 seconds later when Kerfoot backhanded a loose puck past Halak for his third.
Andersen faced 33 shots through two periods, and the Boston kept coming late in the third, with Pastrnak tying things with 4:26 left in regulation when he blasted a one-timer for his ninth.
Pastrnak now has nine goals on the season, including seven in the last three games, which puts him in a tie with Edmonton's James Neal for the NHL lead.
The Bruins, meanwhile, were minus veteran center David Krejci (upper-body injury) for a third straight game.
Toronto has lost to Boston to open the playoffs each of the last two years — with both series going to a Game 7 — but with Tavares, Zach Hyman (knee) and Travis Dermott (shoulder) all out injured, and some major roster restructuring in the off-season, just nine of the 18 skaters who dressed for the Maple Leafs in the deciding game back on April 23 were in Saturday's lineup.
The Bruins, who went onto make the Stanley Cup Final before losing on home ice in Game 7 against the St. Louis Blues, dressed 13 skaters from that 5-1 victory against Toronto.
The Maple Leafs opened the scoring at 5:55 of a spirited first period when Rielly's point shot with Johnsson battling in front went in off Bruins defenseman Brandon Carlo and in for his first of the season.
DeBrusk came close to tying the game a few minutes later when he blew past Tyson Barrie, but Andersen made a nice toe save.
Timashov made it 2-0 on a good fourth-line shift from Toronto. The rookie forward got the puck from Frederik Gauthier and moved into the slot before roofing his first NHL goal past Halak.
"It's a dream come true," Timashov said.
The Bruins, who had 18 shots in the first, finally got on the board with 20.6 seconds left in the period when DeBrusk took advantage of some poor defending to beat Andersen from in-close.
Coming off Thursday's 4-3 shootout loss at home to Tampa Bay, Boston fed off that goal in the second and had Toronto on its heels for long stretches.
The Maple Leafs' best chance of the second came after Sean Kuraly threw the puck in front of his own net, but Barrie was robbed by Halak with the glove.
NOTES: Halak, who has shared the Boston crease with Tuukka Rask to start the season, made his fourth start. ... U.S. Open and Rogers Cup champion Bianca Andreescu of Mississauga, Ontario, dropped the puck for the ceremonial faceoff. ... Attendance was 19,394. ... Babcock threw an early curveball with Tavares out after going through Friday's practice and Saturday's warmup with Matthews centering William Nylander and Andreas Johnsson, and Alexander Kerfoot between Marner and Ilya Mikheyev. Babcock instead started with Matthews-Marner-Johnsson and Kerfoot-Nylander-Mikheyev, and tinkered with his top-6 at times throughout the night. Johnsson left in the second period after blocking a shot and didn't return.
Bruins: Host Toronto on Tuesday night.
Maple Leafs: Host Columbus on Monday night.
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