Unbeaten heavyweight champion Deontay Wilder once boldly claimed he could knock out Mike Tyson in his prime.

In 1986, Tyson became the youngest heavyweight champion in history after beating Trevor Berbick at the age of just 20 years and four months.

Wilder, who became the first American world heavyweight champion in nine years when he captured the belt in 2015, confidently told TMZ how he thought the fantasy bout would go.

"Me vs. Tyson in '86, I'd kick the hell outta that guy.

"Listen, I've got to keep it real. I know people always go back to the old school or look at the new school and there's no school where I'm not No. 1 on earth."

Despite boasting an impressive 41-0 record with 40 knockouts, Wilder received criticism for his claims from the likes of British boxing legend Lennox Lewis.

"I just heard Deontay Wilder said he would destroy a young Mike Tyson. My thoughts are that it's easy to talk until you actually get in the ring."

Lewis held the WBC, WBA and IBF crowns, and stopped Tyson in his penultimate bout in June 2002. Speaking on his social media, Lewis said he's yet to see Wilder face someone as impressive as Tyson.

"I like Wilder but he's never been in there with someone that ferocious who truly wants to break his ribs with every punch. I don't see it!

"I love Deontay Wilder's confidence. You need that to sit atop the heavyweight division. He's hungry and shows up in probably the best shape in division but there are levels to it and he's still adding to his arsenal.

"My best advice to the entire crop of young heavyweight champs is to focus on being the best of YOUR era out of respect and reality. It's unprovable. Of course people asked but I found no need to speculate or compare myself to my idol [Muhammad] Ali or any other of the past greats.

"History will decide your place among the all-time greats so go out there, clean up the division, defend your title, reign supreme and your work will speak for itself."

Wilder is next in action against Luis Ortiz, defending his strap on March 3.