Dana White ain't exactly saying "never" when it comes to Greg Hardy possibly fighting in the UFC ... but the ex-NFL star has to prove himself in some "serious fights" before he gets a look.
Hardy -- who was a beast in the NFL -- has transitioned into MMA and vows to be a real deal fighter ... with hopes of one day competing in the Octagon.
White warns that athletes who come from other sports often get WRECKED when they try to fight ... since most successful MMA fighters have been training for combat since they were kids.
Is Hardy the exception to the rule? We'll see ...