After Anaheim failed to clear the puck out of its own zone at the right point, Matt Hunwick found Landeskog with a short pass and the 19-year-old fired a high shot to the short side of Ducks goalie Jonas Hiller for the game-winner.
Kevin Porter and Jamie McGinn also scored while Semyon Varlamov turned aside 38-of-40 shots for the Avs, who grabbed sole possession of the eighth and final Western Conference playoff spot with the victory.
Hiller finished with 30 saves for Anaheim.
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