via Terry Frei of the Denver Post,

The Avalanche was down to five defensemen after Nikita Zadorov took a high hit from the Capitals' Tom Wilson to Varlamov's left and, with trainer Matt Sokolowski attending to him, stayed down for a minute or two. He then came to the bench and straight to the dressing room, and was done for the night. The Avalanche said he suffered a head injury.

Someone did yell heads up...