This one could haunt Gabriel Landeskog for a long time.
Sharks forward Barclay Goodrow skated the puck outside his blue line but turned it over before he could get any further. In transition, the Avs came down and scored, capitalizing on the neutral-zone giveaway.
However, while five Avalanche skaters were onside, a sixth - Landeskog - was slow to get off the ice.
Here's a screenshot of Landeskog, who was still standing at the bench as the puck reentered the Sharks' zone.
Although Landeskog was in the midst of a change and clearly not a factor in the goal, by rule, he was still offside.
The NHL later issued an explanation for the ruling.
Had one of Landeskog's teammates opened the gate, or if he hopped over the bench, the goal would've counted.