Former cruiserweight champion Johnny Nelson is expecting a tough outing when WBO, WBA, IBO, IBF heavyweight champion Anthony Joshua makes a mandatory defense against Oleksandr Usyk.

The two Olympic champions will collide on September 25.

Nelson is a very big fan of both Usyk and Joshua.

But, he also feels Joshua's size will be too much after watching Usyk have issues in winning a twelve round decision over division veteran Derek Chisora in October of 2020.

"I've always been a massive fan of Anthony Joshua, it's never been hidden. I'm a fan of Oleksandr Usyk because at cruiserweight I said, 'This guy is the heir apparent. I could see him stepping up to heavyweight and making a massive impression like Evander Holyfield back in the day.' [But he's a] different style of fighter. But then I saw his introduction to the heavyweight division and I was underwhelmed. And he's a good fighter, excellent pedigree," Nelson told Sky Sports.

"Better pedigree than Anthony Joshua as an amateur at least. I think Anthony Joshua will be far too big, far too strong, far too sharp and far too aggressive. And Usyk's gotta depend on his unorthodox style to try and befuddle Anthony Joshua to get through that fight."

At the same time, Nelson does not expect the contest to be an easy fight.

He is not ruling out the possibility of an upset win by Usyk.

"It's not an easy fight. So if anybody tries to say this is a done deal, this is not a done deal. This is a tough fight for Anthony Joshua. So Anthony Joshua needs to make sure he has his wits about him, does not underestimate this guy just because he's a small opponent," Nelson said.

"But he needs to stamp his authority as a big strong, fast, athletic heavyweight champion. In doing that, I expect him to get the win. But it's going to be a rough ride."