Originally published on ProWrestlingSheet.

UFC star Conor McGregor has doubled down on his recent tirade against WWE's current roster ... only this time the outspoken fighter spewed his verbal vomit towards John Cena.

McGregor sounded off Friday during a press junket, after someone asked about Ric Flair saying Conor should have more respect for the wrestling industry due to jacking his gimmick.

The UFC fighter praised The Nature Boy at first and called him a legend. He noted that his demeanor, however, is "the real deal" and not a gimmick.

Conor then took a shot at John Cena out of nowhere ... saying, "he's 40 years of age and he's walking around in a luminous orange t-shirt and a headband talking about nobody can see him.  We can see him right there. He's a big, fat 40-year-old failed Mr. Olympia motherf***er."

As for the others who challenged him -- McGregor adds, "Come at me and see what happens."