Wladimir Klitschko believes Anthony Joshua has more potential than any other boxer he has ever seen - and the unified heavyweight world champion would be open to facing the Briton.
Joshua has gone from strength-to-strength since winning super-heavyweight gold at the London 2012 Olympics. The Londoner remains unbeaten in 13 fights as a professional and has only been taken beyond two rounds twice in his pro career.
Londoner Joshua sparred at Klitschko's training camp last year and, after seeing what the 25-year-old can do, the Ukrainian was left very impressed.
"I've faced a lot of athletes and opponents and in the last 25 years there is one person who has the potential to become a really big star in boxing," Klitschko told BBC Radio 5Live.
"Not only inside the ring but that person, and I'm talking about Anthony Joshua, has qualities that not many guys have had.
"Either they had good skills but not the strength, or they had strength but not the skills. Or they were good inside the ring but not outside because their life outside messed them up and that reflected on their sporting career. He definitely has the potential to become a real big star in boxing."
Klitschko, 39, puts his WBO, WBA and IBF belts on the line against Joshua's fellow Brit Tyson Fury in Germany on October 24.
However, after seeing Joshua become the first man to stop American Kevin Johnson in May, Klitschko hinted he would be open to fighting him - someday.
"He needs to improve and eventually it will happen, if I stay where I am today," Klitschko added.
"You cannot pass me since I've been holding the titles for many years, so if you want to get onto my mountain then you will have to face me."
Joshua is next in action against Gary Cornish in September. The pair will fight it out at London's O2 Arena for the vacant Commonwealth heavyweight title.