Buffalo Sabres left winger Jochen Hecht (55), of Germany, is chased by Toronto Maple Leafs defenseman Brendan Bell (36) behind the Leafs net during the first period of an NHL hockey game in Buffalo, N.Y., on Saturday. (AP Photo/Don Heupel)
Darcy Tucker and Jeff O'Neill also scored for the Maple Leafs, who have won four of their last five.
Jochen Hecht scored for the Sabres, who lost for the first time in regulation since a 4-2 defeat against Philadelphia on April 7. Buffalo opened this season with 10 straight wins before falling to Atlanta 5-4 in a shootout last Saturday.
The Maple Leafs used a three-goal second period to win for only the fifth time in 23 regular-season games in Buffalo since 1996.
Sabres leading scorer Maxim Afinogenov was knocked out of the game in the first period with an upper body injury. He played five shifts, totalling nearly four minutes, before heading to the dressing room.
Afinogenov, with eight goals and 11 assists, entered the night tied with the Thrashers' Marian Hossa for second in scoring in the NHL.
Hecht opened the scoring with his third goal of the season seven minutes into the first period. He outmuscled defenceman Brendan Bell before putting a one-handed backhand past Andrew Raycroft.
Sundin answered just over 10 minutes later, redirecting Kyle Wellwood's pass at the top of the crease past Ryan Miller.
The Maple Leafs broke it open in the second when Tucker, O'Neill and Sundin scored in a 3:24 span midway through the period. Tucker's team-leading 10th goal made it 2-1 at 9:20 with Toronto on a two-man advantage.
The Maple Leafs outshot the Sabres by a 17-4 margin in the period.
Raycroft made 29 saves, including 16 in the third period, in winning his third straight start.
Miller was making his fifth consecutive start, and has allowed four goals in each of his last three starts.
It was Sundin's second multi-goal game of the season, and the big centre has eight points in his last four games.
Notes: Toronto has allowed the opening goal in five of the past six games. . . . The game marked the end of the Maple Leafs' three-game road trip. . . . Toronto forward Alex Steen missed about 11 minutes of the first period when a deflected puck cut his lip, forcing him to the dressing room for treatment.