Patrick Marleau scored twice in the second period as the San Jose Sharks clipped the Maple Leafs 2-1.
The win snapped San Jose's four game losing streak.
It's Toronto's seventh loss in eight games.
Jake Gardiner scored the only goal for the Leafs and James Reimer made 24 saves.
Toronto is now ninth in the Eastern Conference after Winnipeg beat Tampa Bay 4-3 and Florida lost 3-2 in a shootout to Minnesota.
That leaves the Jets one point ahead of Florida for first place the Southeast Division and the third seed in the East.
Florida is eighth in the conference, one point ahead of Toronto.
The Leafs host the Washington Capitals on Saturday night on CHML before they entertain the Panthers on Tuesday.
Washington is three points out of a playoff spot.