The Maple Leafs placed newly acquired center Patrick Holland on their top line between Phil Kessel and van Riemsdyk, which allowed van Riemsdyk to move back to his natural position at left wing. He looked comfortable back on the left side, scoring his eighth and ninth goals of the season in the first period.
At 5:45, van Riemsdyk re-directed a Cody Franson point shot to open the scoring. Then at 13:35, on a power play, van Riemsdyk re-directed another Franson shot to give Toronto a 2-0 lead.
Van Riemsdyk had been pointless in his previous five games, four of those at center.
Kulemin made it 3-0 at 11:49 of the second period on just his third shot on goal of the season. Mason Raymond also scored for the Leafs.
James Reimer made 33 saves to move to 5-2-0 on the season. Jonas Enroth made 18 saves for Buffalo.
Jamie McBain got Buffalo on the board 2:15 into the third with a slap shot, which beat Reimer glove side for his second of the season.
With the Sabres trailing 3-1 in the third, tempers boiled over following a collision between John Scott and Dion Phaneuf. During the next stoppage in play, Phaneuf cross-checked Cody McCormick as the two exchanged words. Toronto's Colton Orr immediately stepped in and was given a 10-minute misconduct.
Scott and Frazer McLaren each received 14 minutes in penalties on the play, ending their respective nights early after taking misconducts. A total of 30 minutes in penalties were handed out during the altercations.
Tyler Ennis got the Sabres within one when he one-timed a Matt Moulson pass for his third of the season past Reimer at 6:11.
Leafs defenseman Mark Fraser left the game with an undisclosed injury after playing five shifts and 3:54 in the first period.
Earlier in the day, Toronto acquired Holland and Brad Staubitz from the Anaheim Ducks in exchange for defenseman Jesse Blacker and a conditional third-round draft pick. Staubitz was sent to the AHL's Toronto Marlies.
Notes: Toronto assigned center Troy Bodie to the Marlies. Leafs center Nazem Kadri served the second game of his three-game suspension for his hit to the head of Minnesota Wild goaltender Niklas Backstrom and is eligible to return to Toronto's lineup Nov. 21. Maple Leafs defenseman Morgan Rielly was a healthy scratch for the fifth time this season.