World heavyweight champion Wladimir Klitschko says Britain's Anthony Joshua is the most promising boxer he has seen "in 25 years".
Londoner Joshua, 25, is undefeated in 13 fights since turning professional after winning Olympic gold in 2012.
WBA, IBF and WBO champion Klitschko, who has trained with the Englishman, said: "Joshua has the qualities that not many guys have had.
"He definitely has the potential to become a real big star in boxing."
In May, Joshua beat American Kevin Johnson, who had not been stopped in 36 previous fights.
Johnson had also gone the distance with Wladimir's brother, Vitali, a former world champion.
Klitschko, who fights Britain's Tyson Fury in October, said he was also impressed by Joshua's all-around attitude.
"Anthony has all the tools to become that great champion inside and, most importantly, probably, outside of the ring," said the 39-year-old.
The Ukrainian, who has not lost a bout in 11 years, added that he "could not exclude" the chance of fighting Joshua in the future.
"He needs to improve and eventually it will happen, if I stay where I am today." Klitschko told BBC Radio 5 live.
"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."
Listen to the full Klitschko interview on the 5 live boxing podcast.