As it turns out, it's because he was playing with a hand injury,  according to The Denver Post  . 

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Avs beat writer Adrian Dater, with the help of Twitter tweets, suggests the injury happened during Game 3 when Landeskog was slashed by Wild forward Matt Cook.

It was the 21-year-old's first Stanley Cup playoffs. He scored three goals and four points in the seven-game series, which the Avs lost. Due to the injury, Landeskog has declined an invitation to play with Sweden in the World Championships.