London - Roger Federer says Alexander Zverev has the "full package" as the young German bids to establish a foothold at the pinnacle of the men's game and push the old guard aside.
Zverev, who lost in three sets to Federer at the ATP Finals on Tuesday, has climbed to number three in the world after a breakthrough season in which he has won five events, including two Masters tournaments.
The towering 20-year-old is being spoken about as the leader of a pack of young tyros eyeing their chance to unseat the game's ageing aristocracy.
Having beaten Federer earlier this year at the Rogers Cup in Montreal, Zverev went toe to toe with the Swiss great in their round-robin encounter at the O2 Arena, taking the match to a third set before he lost his way but he can still reach the semi-finals.
"I like what I'm seeing with Sascha (Alexander)," said Federer. "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."
Federer said younger players in general were taking longer to make their mark in the modern game, with most of the major trophies locked down by the "Big Four" of Federer, Rafael Nadal, Novak Djokovic and Andy Murray over many 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 even though I'm really happy to see that there is the likes of (Denis) Shapovalov or Nick (Kyrgios), now also Zverev, making the move early, like what Rafa and Andy did, Novak, 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."
With Djokovic and Murray missing from the end-of-season showpiece and Nadal having pulled out injured, there is a chink of light for Zverev and the other players in the eight-man London event, even if Federer is a big obstacle.
The Swiss thinks whatever happens this week, the experience is going to stand Zverev in good stead for the future.
"He's already three 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."
Roger Federer says Alexander Zverev has the "full package" as the young German bids to establish a foothold at the pinnacle of the men's game and push the old guard aside.