Tuesday night fight ends in devastating knock out.

This one is hard to watch.

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One former National Hockey League player learned the hard way that the boys in the AHL can hit.

Brian McGrattan, now a member of the San Diego Gulls, was knocked out cold, and stayed down on the ice for several long moments after a devastating punch from San Antonio Rampage's Daniel Maggio.

Perhaps what truly caused McGrattan to be so seriously separated from conciousness was the additional damage he suffered when he crashed face first into the ice, thanfully he would regain conciousness and was taken to hospital for treatment.

Warning the video below is brutal.