When hockey players first learn how to play the game, one of the first lessons is to keep your head on a swivel.

While checking and open ice hits are not permitted until high school in many youth leagues, the general ability to use peripheral vision to put yourself in a non-susceptible position on the ice is a necessary one.

At the NHL level, not keeping your head on a swivel can cost you your health, your career and even your life.

In recent years, some of the most memorable, and dangerous, hits have come on the open ice, as unsuspecting players have been gravely punished with brutal hits.

Over the weekend, Colorado Avalanche enforcer Nikita Zadorov absolutely annihilated Mark Scheifele of the Winnipeg Jets not once, but twice, in the same game.

Check out the hits in the video below.

While the first hit was extremely forceful, the second one was extremely violent and borderline dirty.

Notice that Scheifele put his head down prior to the hit, which left him wide open for punishment.

His Jets teammates immediately pounced on Zadorov and a fight ensued, but the damage had been done. Jacob Trouba was able to land a few punches on Zadorov before they were separated, though.

Say what you want about the NHL, but the permitted violence and fighting makes it extremely exciting to watch over some other competing sports.

As a result, you can label hockey players as some of the toughest athletes on Earth.