He's in awe of Nick Kyrgios's "sick power", but Roger Federer has urged Australia's mercurial young tennis star not to wind up as a wasted talent.
"I just think the next couple of years are going to be so crucial for him," Federer said while calling for the Australian public to also cut Bernard Tomic some slack.
Federer has been a Kyrgios fan since the pair practised together in Switzerland before the Canberran's breakout run to the Wimbledon quarter-finals in 2014.
"I was already unbelievably impressed at his sheer power, his talent, his potential," said Federer.
"It goes way back. He's enjoyable to watch. I know some people might not like it. I like it. He's got a lot of personality.
"(He) might take it (too) far to some extent, but I think he's a great player.
"He's got sick power, and it's going to take him a long way."
Provided Kyrgios - already a two-time grand slam quarter-finalist but set to drop outside the world's top 40 after his third-round Australian Open exit - realises "how important the next couple of years are" and knuckles down.
"Otherwise the train leaves the station and you're maybe not on it," Federer said.
"It would be a pity to waste talent and all that, even more so in this day and age because I feel talent brought you further back in the day.
"Just talking about a guy who has talent and potential, I can't hear it anymore.
"Too many guys have talent. Too many guys are working hard. I don't believe in that very much anymore."
A racquet-smashing tantrum thrower himself early in his grand career, Federer empathises with Kyrgios, whose image has taken a battering over the past six months.
"It just takes time for people to get to know you. I had the same thing," Federer said.
"I felt very misunderstood many times when I was younger.
"I felt like I had to put in a lot of work with the press so they first knew who I was so they could relay the messages to the public, the broader public, the right way.
"So in a way I always feel like it's really interesting and nice to see a youngster grow up in the public eye.
"But then at the same time, you also have the negatives. He's fighting that a little bit.
"But he's doing okay now, better now.
"He needs to, obviously, for what happened last year."