It’s been a long but rewarding season for Roger Federer, but even between winning trophies, the Swiss supremo has an eye for the next big thing to hit the ATP scene.

And the new kid on the block from Germany has certainly impressed Federer this week during the ATP Finals in London.

The 19-time Grand Slam champion was taken to three sets by the 20-year old German Alexander Zverev at the O2 Arena, and the man who has won eight Wimbledon crowns was impressed with the application of the world number three on the court.

“I like what I’m seeing with Sascha,” said Federer following the bout. “I see somebody who is working towards the future.

“I think, yes, of course it’s really important right now to have success. He had that with two massive wins in Rome and Montreal. I mean, that’s going to protect his season anyways. The rest sort of is all a bonus.

“What I like to see is I feel like they’re working towards how he could be playing when he’s 23, 24 years old in terms of fitness, planning, organisation, all these things. I think that’s nice to see.”

It isn’t just the mercurial Zverev who has captured the attention of the tennis great though.

Controversial Aussie Nick Kyrgios and teenage Canadian Denis Shapovalov have also come in for praise from Federer, but has warned that patience is a virtue when it comes to developing their craft over the years.

“Now, the future? The thing is it seems like they need a bit more time, the young guys in general, to break through these days,” Federer stated.

“Even though I’m really happy to see that there is the likes of Shapovalov or Nick, now also Zverev, making the move early, like what Rafa (Nadal) and Andy (Murray) did, Novak (Djokovic), Lleyton (Hewitt), all these guys. They were such great teenagers.

“I do see a great upside from all these three guys.

“What I like about Zverev is he’s got the full package,” added the six-time ATP Finals winner. “He’s already 3 in the world.

“I think he’s going to leave the World Tour Finals, regardless if he qualifies for the semis or not, with a lot of information.

“I think the last six months of the season gave him everything he needs to work forward to. ‘Then, of course, he’s only going to get stronger from here. That should be very encouraging for him and his team.”