Comeau was standing to the right of the net when Martinek unleashed a slap shot from the point, directing it past James Reimer to hand the last-place Islanders only their third win in eight games.
Tim Brent had a goal and an assist while Keith Aulie scored his first NHL goal and Nikolai Kulemin added a score for the Maple Leafs, who gained one point in their push for a playoff spot.
The Leafs entered the game three points behind Carolina for the final Eastern Conference post-season berth.
Reimer turned aside 36-of-40 shots for Toronto.
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