Roger Federer predicted earlier this week that it would be difficult for the Big Three (Novak Djokovic, Rafael Nadal and himself) to keep dominating at the Grand Slams next year, as the next generation of players are now "playing with the big boys, and being really able to challenge and beat us".
His prediction materialised in some way at the Rolex Shanghai Masters yesterday.
The world No. 3 was beaten 6-3, 6-7 (7-9), 6-3 in the quarter-finals by 22-year-old Alexander Zverev in a 2hr 4min encounter that saw him lose his cool after receiving a point penalty - his first in a "long, long time".
Earlier, world No. 1 and defending champion Djokovic lost 3-6, 7-5, 6-3 to 21-year-old Stefanos Tsitsipas.
World No. 6 Zverev had five match points in the second set, the last of which Federer saved with a backhand passing shot. The 38-year-old Swiss served an ace to force a third set, during which he was penalised in the fourth game for twice hitting the ball out the court in anger.
Federer appeared to have a lengthy argument with chair umpire Nacho Forcadell at the changeover, saying: "I've got other issues man, I'm missing shots."
The 20-time Grand Slam champion declined to state the reason for his unhappiness with Forcadell during his post-match press conference, but said of his opponent: "I told him at the net that he showed great character, that he was strong... I thought he didn't show any frustrations or too much negativity.
"That was impressive because he has tendencies to get a bit down on himself, especially this season he hasn't been playing so well, so that impressed me the most."
Zverev, who plays Matteo Berrettini next, believes the outcome is "very important mentally" and gives him the confidence that he can put away the best in the trade.
He said: "The five match points I had in the second set - them going away and still knowing I can win in three sets is very important, especially against someone like Roger because normally he doesn't let go of these kind of matches."
World No. 7 Tsitsipas, who qualified for his maiden year-end ATP Finals yesterday, is the youngest player to defeat each member of the Big Three.
"I always dreamt of beating those players and I see each match when I go out on the court as an opportunity to bring the best out of me. It's a very big boost," he said.
He hit 34 winners to Djokovic's 28, and made 22 unforced errors while his opponent had 26.
Said the 32-year-old Serb: "I wasn't sharp. I lacked that little bit of dynamic movement and acceleration in my shots... I just gave him enough time to really dictate the play from the back of the court and he deserved to win."
Tsitsipas' next opponent is Russian Daniil Medvedev, whom he has never beaten in four meetings.
The Greek said: "I hope it's going to be a fresh, new Stefanos out on this court, showing his best tennis and playing smart and making him play out of his comfort zone."
S-finals: StarHub Ch201, 4pm & 8pm