Roger Federer hailed Alexander Zverev as the complete package after beating the German up-and-comer to book his place in the last four of the ATP Finals.
The 20-year-old Zverev showed London’s O2 Arena why he will surely become a star of men’s tennis one day but Federer’s own time is far from finished yet and his class eventually told.
Sixteen years and 19 grand slam titles separate this pair but remarkably it was Federer’s legs that were fresher in the decider, and after two hours and 11 minutes he had won 7-6 (8/6) 5-7 6-1.
It means the 36-year-old is certain to move into this tournament’s semi-finals, even before his final group match against Marin Cilic, while Zverev faces American Jack Sock for the second qualifying spot.
Zverev is yet to make an impact at a grand slam but if the world number three overcomes Sock, a Federer reunion in Sunday’s final would seem a distinct possibility.
"What I like about Zverev is he’s got the full package," Federer said.
"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."
Federer remains the favourite to claim a record-stretching seventh title here, even more so after Rafael Nadal became the latest top player to pull out on Monday.
Nadal joins Andy Murray, Novak Djokovic, Stan Wawrinka, Kei Nishikori and Milos Raonic on the sidelines but Federer believes the game’s injury epidemic simply comes down to age.
"A lot of the guys are just touching 30 plus," Federer said.
"Back in the day, at 30, a lot of guys were retiring - (Stefan) Edberg, (Pete) Sampras - it was like normal at 29 to 32, to start looking towards the end of your career.
"Now people expect everybody to play till 36 and when somebody is injured at 31, it’s like, ’Oh, my God, how is this possible?’ Actually, it’s a normal thing."
Zverev might rue missed opportunities, having squandered a set point and 4-0 tie-break lead in the first set, but it was concentration and stamina that ultimately proved the difference.
"I think it was a very positive match," Zverev said. "Obviously he won it, he’s in the semi-finals, but even for me, I played the better match of the two today.
"I think I still have great chances of qualifying, playing Jack Sock next. I think if I continue having this level, I don’t know, maybe you’ll see me on the weekend still."
Earlier in the day, Sock kept his hopes of progress alive by defeating Cilic 5-7 6-2 7-6 (7/4). Federer’s victory means Cilic is eliminated.