Without the benefit of taking part in his first formal practice in the five days since being traded to Toronto, centre Ryan O'Reilly has found instant chemistry with his new Maple Leafs linemates.

O'Reilly scored twice on Toronto's first two shots on net and added an empty-net goal to cap a career-best five-point outing in a 6-3 win over the Buffalo Sabres on Tuesday night.

"Yeah, it's been crazy, though, I think a lot of adrenaline, too," said O'Reilly, after playing his third game with Toronto since being acquired in a trade with St. Louis on Friday.

O'Reilly scored 37 seconds apart in an opening period the Maple Leafs led 4-0 on goals scored in a span of 8:18. And after Buffalo surged by scoring three times to cut the lead to 5-3 on Jeff Skinner's goal with 3:31 remaining, O'Reilly sealed the win when his shot dribbled into the net with 1:10 left.

O'Reilly's new linemates got in on the fun, with captain John Tavares scoring and adding three assists, and Mitchell Marner setting up five goals. Marner's five assists tied a franchise record for most in a road game, shared by Pep Kelly, Babe Pratt and Borje Salming.

Michael Bunting and William Nylander also scored in a game played before a large contingent of "Go, Leafs! Go!"-chanting, blue-and-white clad fans who made the trip across the border.

WATCH | Newly acquired O'Reilly helps Maple Leafs defeat Sabres:

Ilya Samsonov, who didn't face his first shot until halfway through the first period, finished with 29 saves.

Alex Tuch, with the 100th goal of his career, and Jack Quinn also scored for Buffalo.

Ukko-Pekka Luukkonen allowed four goals on 10 shots before being yanked after getting beaten on the short side by Bunting 12:09 in. Struggling in his bid to win a three-way goalie competition, Luukonen has allowed 19 goals in dropping to 1-3-1 in his last five starts. He was replaced by Craig Anderson, who allowed one goal on 18 shots.

"We got to forget about this one. Yup, we can't play like that in the first 10 minutes," said Sabres defenceman Rasmus Dahlin, who was also bothered by seeing so many Maple Leafs fans celebrating O'Reilly's third goal by littering the ice with hats.

O'Reilly's offensive outburst came in a homecoming for the two-way centre, who spent two seasons playing for the Sabres before being traded to St. Louis in July 2018.

The playoff MVP for the 2019 Stanley Cup-winning Blues opened the scoring 3:51 in by snapping in Marner's centring pass into the open left side of the net. Set up by Marner again, O'Reilly broke in alone and backhanded a shot, beating Luukkonen on the short side 37 seconds later.

"They were just at their best from the start," Maple Leafs coach Sheldon Keefe said of a newly formed second line that features Tavares shifting to wing with O'Reilly taking over at centre. "I thought that line, our team in general, our team game in that first period, that's as dominant as we've been all season long, so it's tremendous to see."

Maple Leafs host the Minnesota Wild on Friday before departing for a five-game trip.

Sabres travel to play the Tampa Bay Lightning on Thursday.