World number one Novak Djokovic suffered a quarter-final exit against Russian Daniil Medvedev at the Monte Carlo Masters.
The 31-year-old, winner of the event in 2013 and 2015, lost to the world number 14 in two hours, 20 minutes.
Medvedev faces another Serb in the last four, world number 48 Dusan Lajovic.
Defending champion Rafael Nadal, seeking an unprecedented 12th Monte Carlo title, plays Argentine world number 35 later on Friday.
Djokovic won a record seventh Australian Open title in January but lost in the third round at Indian Wells and the fourth round in Miami last month.
He had beaten Medvedev in the last 16 en route to his Melbourne triumph, but lost his serve five times as the 23-year-old 10th seed recorded his first victory against the 15-time Grand Slam champion in their fourth meeting.
In the doubles, Britain’s Jamie Murray, third seed with partner Bruno Soares, moved into the semi-finals with a 7-5 6-2 win over Diego Schwartzman and Joao Sousa.
Murray and Soares will play Dutch pair Robin Haase and Wesley Koolhof, who beat top seeds Pierre-Hugues Herbert and Nicolas Mahut in the opening round.
Meanwhile, British number one Johanna Konta is hoping for more of the home-crowd energy that pulled her back from the brink of exhaustion in their last tie as her team bid for Fed Cup promotion.
Britain face Kazakhstan in a best-of-five play-off at London’s Copper Box Arena this weekend hoping to end a 26-year wait to reach World Group II.
It is the fifth time in eight years GB have reached the play-offs and every previous tie has been away from home, with defeats keeping them in the third tier of women’s team tennis.
This year, they earned their place with victory in February’s round-robin event in Bath, where Konta battled fatigue and needed to be helped to her feet at the end of her match in the decisive win against Serbia.
“The home support lends you energy when you need it,” said Konta, 27. “You really feed off their emotions and their desires for you. It is also the team you have behind you.”
Konta’s world ranking has dropped from 23 to 46 in the past 12 months, but she made changes to her coaching team in November and reaped the rewards with a determined performance in Bath.
“Overall, I feel good about the work I am putting in with my own team,” she said. “I am enjoying my tennis and enjoying my life, so it’s a good position to be in.”
