Deontay Wilder has responded to Tony Bellew calling him the 'worst heavyweight champion of the world'.
As well as down-playing Wilder's skills, Bellew also reckons Joshua - who holds the IBF, WBA (super) and WBO heavyweight titles - is the best out of the lot.
"AJ is the best heavyweight in the world," the ex-cruiserweight world champion said. "Physically, athletically, everything. He is fast and explosive. He is the perfect role model. To look at where he has come from to where he is now is incredible."
"The worst, least technically gifted heavyweight champion ever," he said about Wilder.
"Deontay Wilder is the worst heavyweight champion of all time. Technically, I don't think there has ever been a worse champion.
"This man can't throw a proper combination. This man hits the lights when he throws a right hand. He is ultimately a one trick pony. Don't get me wrong, it's a fantastic trick, but it is just one. He has been exposed at the top level."
The WBC holder has since responded and he didn't hold back.
"You know Tony Bellew a bitch," Wilder said. "He was scared during that time and he's scared now.
"I'll still go down in weight. I can still lose weight. One thing I know how to do is go down.
"Any of these clowns around here wanna try Deontay Wilder, give me a chance? Meet me at a catchweight.
"Sometimes it's about principle. This is a principle ass whooping right here. This is just because.
"If Bellew ever wants this, if he ever wants this work, let me know. I'll get down or you can come up, whatever you comfortable with."
Meanwhile, the undefeated-American is set to defend his belt against Dominic Breazeale on May 18th after failing to agree terms with Tyson Fury.