Fourth seed Alexander Zverev suffered his latest grand-slam disappointment with a bad-tempered fourth-round loss to Milos Raonic at the Australian Open.
The 21-year-old beat Roger Federer and Novak Djokovic back-to-back to win his biggest title at the ATP Finals in November.
But he was unable to improve his record of having reached only one slam quarter-final as he suffered a heavy 6-1 6-1 7-6 (5) defeat to resurgent Canadian Raonic.
After breaking serve in the opening game of the match, Zverev incredibly lost 12 of the next 13 games and showed his frustration by destroying his racket after going 4-1 down in the second set, smashing it repeatedly on the ground.
He produced a better effort in the third set and saved two match points at 4-5 but Raonic, who began his tournament by beating Nick Kyrgios and Stan Wawrinka, was ultimately too strong.
"I played bad," said Zverev. "The first two sets especially I played horrible. It's tough to name one thing. I didn't serve well, didn't play well from the baseline. Against a quality player like him, it's tough to come back from that."
There was no doubt about Zverev's commitment to smashing his racket, eventually flinging the mangled mess of metal and string dismissively to the court.
"It made me feel better," he said. "I was very angry, so I let my anger out."
Zverev has become all too used to the narrative that he has under-performed at the slams and this performance felt all the more disappointing after his success at the O2 Arena.
But the German believes winning that title may have hampered his chances here, saying: "I didn't have a very long off-season, didn't have a lot of rest. But this is us as tennis players. I'm happy how the season ended. I wouldn't want it the other way."
He has been seen as very much the leader of the next generation, and his results across the board reflect that, but an increasing number of different young players are going further than him at the majors.
Here, that includes his good friend Frances Tiafoe and, of course, Stefanos Tsitsipas, who stunned Roger Federer on Sunday.
Discussing the rivalry among the group, Zverev, who is coached by Ivan Lendl, said: "I was happy for Foe, obviously I'm very close to him. I'm happy that the other young guys are doing well, as well. Nothing but the best for them.
"This is one of many tournaments. You can't really compete every single week saying you made semis there or quarters there, beat that. I want to be the best, but not this week."
Raonic believes he could be benefiting from his incredibly tough path through the draw.
He said: "It's not fun necessarily before the tournament starts to look at it and say, hey, you play Nick to most likely play Stan in the first two rounds. You're hoping for a bit more time to really work your way into things.
"But then on the other end of it I dealt with those challenges really well. Right now I'm here playing some extremely good tennis, I believe. Hopefully I can make that count."
Raonic arrived in Australia two years ago looking like the man most likely to break the stranglehold of the big four after reaching the Wimbledon final and finishing the year ranked world number three.
Two years of repeated injury setbacks have sent him back down the pecking order, but he believes he is a better player than he was in 2017, even if the knocks have taken their toll.
The 28-year-old said: "I think back then I just found some situations a little bit easier to deal with, because I had three or two good years and you don't have to think about things as much. Instinct takes over when you have played that many matches consecutively. I was trusting a lot more."
