After exercising his no-trade clause to veto any potential deal away from Toronto with Tuesday's deadline looming, Mats Sundin scored on the power play in the first period.
The Maple Leafs converted each of their first three opportunities with the man advantage.
Pavel Kubina and Dominic Moore scored even-strength goals in the second as the Maple Leafs beat Ray Emery four times in the middle period to seal Toronto's third straight win against its provincial rival.
Maple Leafs defenseman Tomas Kaberle stopped Mike Fisher's shot at a wide-open net with 1:02 remaining to preserve Toskala's 11th career shutout.
Toronto has won four of five.
Emery stopped 16 of 21 shots in the first two periods for Ottawa, which blew an opportunity to regain the Eastern Conference lead.
The Senators, who got off to an NHL record 13-1 start, remain atop the Northeast Division with 78 points, one less than New Jersey, which took over the conference lead Sunday.
Martin Gerber replaced Emery after the second session and stopped all six shots.
Sundin released a statement Sunday that he would exercise his no-trade clause to veto any deadline deal and remain with Toronto, which is last in the Northeast with 63 points and on the verge of missing the playoffs for a third year in a row.
The Maple Leafs captain opened the scoring on Toronto's first power play 8:19 in when he deflected Kaberle's shot past Emery from the left side of the net.
Tucker made it 2-0 when he scored the Maple Leafs' second straight goal with the man advantage. Kubina got Toronto's third goal and Tucker increased the lead to 4-0 with his second goal of the game and 14th of the season with 2 seconds remaining in Jason Spezza's minor for interfering with Toskala.
Moore scored the Maple Leafs' fourth goal of the period.
SABRES 4, FLYERS 3, SO
In Buffalo, N.Y., Daniel Briere scored the clinching shootout goal in helping the Philadelphia Flyers snap a 10-game losing streak by beating Buffalo.
With a chorus of boos raining down on the Sabres' former co-captain, Briere skated in on Ryan Miller, making a series of back-and-forth moves, before stuffing the puck just inside the right post. The goal came in Briere's third game against his former team since signing with Philadelphia last July.
R.J. Umberger, who capped the Flyers' three-goal comeback with 7:15 left in regulation, Jeff Carter and Scott Hartnell also scored for Philadelphia.
The Flyers snapped an 0-8-2 skid --- matching the longest losing streak in franchise history. --- and won for the first time since a 3-2 victory at Atlanta on Feb. 5.