Anthony Joshua would "hands down" beat Tyson Fury but may find life tough in a fight against Deontay Wilder, according to Wladimir Klitschko.
Ukrainian Klitschko hung up his gloves after last year's stoppage loss to Joshua, who went on to add the WBO strap to his WBA and IBF titles by out-pointing Joseph Parker in March.
Fury previously held all three heavyweight belts after beating Klitschko on points in November 2015, though he has not fought since that famous triumph in Dusseldorf in November 2015.
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The 29-year-old is scheduled to make his long-awaited ring return on June 9, a move that increases the possibility of a money-spinning bout against fellow undefeated fighter Joshua at some stage in the future.
However, having faced both men during his distinguished career, Klitschko is in no doubt over the outcome of a potential all-English showdown.
"Hands down, Joshua [wins]. He is getting to be the complete fighter," Klitschko said in an interview with the Times.
"Technically, size-wise, weight-wise, power-wise. And he is a good learner. The other guy [Fury], like a fart in the wind it is there and it is gone.
"In the history of boxing there are a lot of examples of this kind of guy. They can be successful for a time but are not disciplined enough to continue to be successful.
"I wish Tyson well but I think there is a lack of discipline there, and discipline is more important than motivation. Motivation comes and goes, discipline remains.
"I am not Nostradamus, I can't predict the future, but drawing from my experience I would say it is going to be very difficult for Tyson because there's that lack of discipline."
WBA champion Wilder holds the one major belt Joshua is yet to possess, and Klitschko believes the American's size and speed would make him a handful for his former foe.
"It would be a dangerous fight for Joshua. I'm not saying he wouldn't win it but Wilder has something," Klitschko added.
"Due to his weight, he is extremely fast. He has good power in his hands and he's extremely fast. Maybe he's kind of wild in his technique but those punches are coming from who knows where.
"He is hard to defend against - where is that punch going to land or which side is it coming from? Joshua has all-around more capability but Wilder is taller than Joshua and is faster than Joshua.
"He doesn't have the weight behind his punches but he is extremely fast, and it would depend upon what kind of mood both fighters were in."