The 42-year-old UFC legend expanded on his hate for Jake on ESPN's "DC and Ariel" earlier today ... saying he will NOT step in the boxing ring with Paul.
"Floyd Mayweather is the greatest boxer of all time. So you go and play on his playing field. Why would I go and box Jake Paul?" DC said Monday.
"Who I am doesn't make me chase anything. I made my money as the heavyweight champion of the world. I don't have to chase a payday."
BUT -- if Jake REALLY wants to test his luck, DC says he's down to teach him a lesson in the Octagon ... and it ain't gonna be pretty.
"If he wants to actually fight with me, fight me in mixed-martial arts," Cormier said ... adding he'll even cut all the way down to 205 pounds for the bout.
"This is not going to be fun. I'm telling you right now, at 42 years old -- bad back and everything -- I'm going to torture him. I'm going to hurt him. I don't want to box him. I don't want to fight in a limited skill set of rules."
"If you really want to fight me, fight me in a mixed martial arts competition."
DC went on ... "I'm going to smash him and I'm going to hurt him and then he can go back to fighting these YouTube kids."
Cormier says he won't let Paul use his name as a "springboard" ... and will continue to defend his legacy -- even if it means beating the hell out of an internet superstar.