By Edward Chaykovsky

According to former division king Wladimir Klitschko, his upcoming fight with IBF heavyweight champion Anthony Joshua is the "toughest challenge" of his entire career.

Joshua has steamrolled through nearly every opponent on his undefeated 18-0 record. Only two fighters, Dillian Whyte and Dominic Breazeale, have been able to make it to the seventh round.

Both boxers are Olympic gold medal winners with large fan followings in their respective countries. But even Klitschko, who sold out numerous stadiums in his long career, has ever tackled the task fighting before a massive crowd of 90,000.

Klistschko, who is going to be 41 years old when he enters the fight, has been inactive since losing shocking twelve round unanimous decision to Tyson Fury in November of 2015. That was the first defeat for Klitschko in over a decade and he will enter the ring with his longest stint of inactivity.

For his part, Joshua has fought four times in that time period - with stoppage wins over Charles Martin, Breazeale, Whyte and Eric Molina. Klitschko, even at this stage, is on another level (or several levels) when compared to Joshua's past opponents.

“This fight is definitely something we are thinking is going to be great on both sides,” said Klitschko, speaking to talkSPORT’s Kick Off Boxing show.

“One Olympic champion fighting another, one generation fighting another generation. There are lots of questions. Have I still got it? Is Anthony good enough now? The interest is tremendous, it is amazing, and I am really happy about it. For me it is an upgrade in my career as a fighter - to fight on the biggest stage I have ever had in front of 90,000 people.

“It is the toughest challenge I have ever had.  He is a copy of me in certain ways, size-wise, and is a world champion.”