LONDON • A year ago, Stefanos Tsitsipas won the Next Gen title in Milan - the ATP Tour's showcase event for up-and-coming players.
But in his two matches in the main event so far in London, he has already bolstered the impression that he has the quality to start collecting Grand Slam titles.
While the 21-year-old - the first Greek player to qualify for the elite eight-man season-ender - is still in the first flush of youth as the youngest contestant at this event, he is playing beyond his years.
He crushed defending champion Alexander Zverev of Germany 6-3, 6-2 on Wednesday night to book his semi-final place with a match to spare in Group Andre Agassi.
The debutant backed his opening round-robin win over Russia's Daniil Medvedev with another virtuoso performance at the O2 Arena and has yet to lose a set.
His all-court game, with a big serve, aggressive groundstrokes, deft volleys and silky movement, have made him an instant crowd favourite in London.
All those weapons were on display against 22-year-old Zverev in what was the youngest - in terms of combined age - match at the ATP Finals.
The form of Monday's group-stage victory against top-ranked Rafael Nadal deserted the German as Tsitsipas beat him for the fourth time in five matches.
The Greek later revealed that he had needed a pain-killing injection to play on, but insisted he had no plans to take his foot off the gas against Nadal today, despite having already progressed.
The Spaniard must beat Tsitsipas to secure a last-four berth and keep alive his hopes of landing his first ATP Finals crown.
His opponent, however, wants to claim the scalp of the 19-time Grand Slam winner, who leads their head-to-head record 4-1, and feels that eliminating Nadal is "a good thing to have in your portfolio".
Tsitsipas said: "I'm going to give it my all. I'm going to try to give my soul, and it's also a very good challenge.
"I always find an extra motivation, an extra reason to play well against the top guys. You have been watching them on TV. You have always wanted to be part of that.
"When you see something that you have been dreaming of, there is always a spark, kind of an extra reason to play."
Like Nadal, Zverev must now win his final round-robin match with Medvedev to stay in contention for back-to-back ATP Finals titles.
His sloppy display - he had 18 unforced errors, won just five out of 12 points at the net and had only 28 per cent of second-serve points - was in stark contrast to Monday.
His performance also led retired British-Canadian player Greg Rusedski to slam him as "meek".
He told Amazon Prime: "If I was Sascha, I would watch Medvedev v Rafa, and see what the very best do because he has the potential, but mentally, he let himself down especially in that second set."
Zverev denied yesterday he was using his phone illegally despite TV footage that circulated on social media appearing to show him touching something in his bag at a changeover during the match.
Rules state players cannot access any electronic devices during matches and he claimed he did not have his phone with him on court.
Asked about it, he said: "I always leave it there (in the locker room). I don't know what they saw, but it was definitely not a phone. I mean, a water bottle, maybe?"
AGENCE FRANCE-PRESSE, REUTERS
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