The reality is ... this was no trash-talking, expletive-filled, racist, ugly sideshow (a la Mayweather vs. McGregor), these guys showed nothing but class and respect for each other.

Of course, Ruiz upset Joshua at Madison Square Garden to win all of his championship belts when they faced off in June -- and Andy says he's motivated to show the world it was no fluke.

Ruiz essentially said he doesn't want to be known as a 1-hit wonder -- he wants to solidify a legacy as one of the greatest heavyweight fighters of all time!!!

Of course, Joshua says he's determined to get his belts back ... and warns Ruiz he won't get the benefit of home country advantage this time around.

So, how will the fight go? Ruiz put it best ... "Two big heavyweights punching each other in the face."