Toronto had not won in Buffalo since Feb. 17, 1999, going 0-5-2 since. But the Maple Leafs continued to get production from the top line of Mogilny, Mikael Renberg and Mats Sundin as they extended the Sabres' longest winless streak in 11 years to 10 games (0-8-2).
Mogilny did his damage in a 2:17 span of the second period, when Buffalo erased a one-goal deficit and took a 3-1 lead.
Belfour was beaten by Tim Connolly with 11:20 remaining but turned aside the other 15 shots he faced in the third period. His biggest stop came with 1:57 to go when he slid left and smothered a deflection by Chris Gratton off a 3-on-2.
Stu Barnes had the other goal for the Sabres, who are two ties or losses from matching the longest winless streak in team history.
While the battle of Northeast Division rivals produced the first sellout of the season at HSBC Arena, half the crowd was rooting for Toronto.