World number four Stefanos Tsitsipas suffered a shock straight-set defeat by American Frances Tiafoe on day one at Wimbledon.
Third seed Tsitsipas, who reached the French Open final earlier in June, was beaten 6-4 6-4 6-3 by the impressive world number 57 Tiafoe on Court One.
It is the third time in four attempts the 22-year-old Greek has exited Wimbledon in round one.
Tiafoe meets Canada's Vasek Pospisil or Spain's Roberto Carballes Baena next.
Elsewhere in the men's singles draw on Monday, world number one Novak Djokovic defeated British teenager Jack Draper 4-6 6-1 6-2 6-2 on Centre Court.
British two-time winner Andy Murray faces Nikoloz Basilashvili, Russian fifth seed Andrey Rublev meets Argentine Federico Delbonis and eighth-seeded Spaniard Roberto Bautista Agut plays Australian John Millman.
Tiafoe stuns Tsitsipas for biggest win of career
Frances Tiafoe has not been beyond the third round at WimbledonTiafoe reached the Queen's Club quarter-finals two weeks ago, but this was the first time he has ever beaten a top-five ranked player.
The 23-year-old held on to his advantage after breaking Tsitsipas' serve in the opening game to take the first set - and made his next breakthrough in the ninth game of the second to take firm control of the contest.
Tsitsipas, beaten by world number one Novak Djokovic in five sets in the Roland Garros showpiece, was unable to respond after losing his opening service game in the third set and an unrelenting Tiafoe took his third match point on the Greek's serve to seal a stunning victory.
"It was one of my best [performances]," Tiafoe said. "From start to finish it was pretty clean. This is what you train for, this is what it's all about.
"I'm not close to where I want to be. Today was big, I definitely needed that. He [Tsitsipas] is going to do a lot of great things."
While Tiafoe contested matches at Queen's and Eastbourne prior to Wimbledon, Tsitsipas arrived at the All England Club without playing on grass since his final defeat on the Paris clay.
"For sure the lack of matches was crucial today," said Tsitsipas. "I was thinking maybe I should have played the week before Wimbledon, either Mallorca or Eastbourne, I'm not sure. Any of these tournaments would have helped get me in a better shape, get my tennis ready for the grass court season.
"The transition from clay to grass, in my opinion, is probably the most difficult one, if not the biggest challenge in our sport. I just wasn't able to adapt, I wasn't able to figure these things out early in the match. You just cannot be defensive on grass. It takes away so much from your game.
"I honestly feel if I could have worked a bit more. If I would have played a bit more on that surface, I'm pretty confident I would have done better."
