Wladimir Klitschko believes Anthony Joshua is "hands down" the better fighter than "fart in the wind" Tyson Fury.
Klitschko (64-5) retired last year following his 11th-round TKO defeat to Joshua in April 2017.
Despite having some success in the fight, which included dropping the Brit in round five, the possibility of a rematch wasn't tempting enough for the Ukrainian who officially announced his retirement in August.
Klitschko also suffered points defeat to Fury back in Nov. 2015, but he considers Joshua the better of the two fighters.
"Hands down Joshua," Klitschko told The Sunday Times. "He is getting to be the complete fighter. 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.
"Drawing from my experience I would say it is going to be very difficult for Tyson because there's that lack of discipline."
Fury hasn't fought since his victory over Klitschko in 2015, but is scheduled to make his return to the ring on June 9.
Joshua's last outing was a points win over Joseph Parker in March 2018.