It's something just about every coach will tell you in sports: never let your guard down. Especially when you're fighting, it's never a good idea to take a second to either taunt your opponent or put your hands down.

Jordan Powell learned this lesson the hard way on Friday night when facing Dominick Reyes. 

Reyes landed a couple of shots on Powell, but as the two transitioned, Powell shook his head at Reyes as to say he wasn't doing any damage.

Then this happened.

Powell collapsed in a heap after Reyes landed a beautiful head kick to win via KO. 

Reyes is now 6-0 with five career knockouts and that was somehow the first time Powell had ever been KO'ed. It just goes to show you that anything can happen in a fight.

Wink of the CBS eye to Bleacher Report