Tyson Fury says WBC world heavyweight champion Deontay Wilder has "no intellect" and "no substance".
The Briton drew with Wilder in December and a rematch against the undefeated American is set for 22 February.
And Fury, who has his first bout in WWE on Thursday, says he already has more fans than his rival in the USA.
"He screams 'bomb squad' a lot and pretends to have a personality, but really he doesn't and there is no depth to him," said the 31-year-old.
"I have already got more American fans than Wilder. For whatever reason, Wilder is not popular in America and people don't like him.
"He has got no substance. He is a loud mouth.
"Behind that there is no intellect. He comes out with random things that don't make sense. I am a trash talker, but sometimes I struggle to put together what he is talking about."
Fury will face Braun Strowman at the WWE's Crown Jewel event in Saudi Arabia on Thursday and was warned against the move by his team because any injury could put his February bout against Wilder at risk.
Wilder, 34, faces 40-year-old Cuban Luis Ortiz on 23 November in his 10th defence of the WBC title.
"Wilder has to get through his fight first injury-free and even win," added Fury.
"He should come through, but Luis Ortiz is a dangerous customer and is not to be overlooked or underestimated.
"For four or five rounds he is one of the most dangerous fighters in the world. He is a 6ft 4in southpaw who can punch hard."