Novak Djokovic's preparations for his French Open title defence suffered another setback Friday when he was defeated by Belgium's David Goffin 6-2, 3-6, 7-5 in the Monte Carlo Masters quarter-finals.
The Serb saved four match points but slumped to his first loss to Goffin after five successive wins on a fifth match point, hindered by a time violation as he prepared to serve.
World number two Djokovic faced 17 break points and saved 13 in his frustrating marathon.
The 29-year-old Serb battled for two and three quarter hours against the 10th seeded Belgian who will now face Rafael Nadal after the fourth seed defeated Argentine Diego Schwartzman 6-4, 6-4 under the floodlights.
Nadal is seeking a record tenth title at the Monte Carlo Country Club and will be the favourite after Djokovic joined world number one Andy Murray and third seed Stan Wawrinka on the casualty list.
"It's just unfortunate I missed my chances in the beginning of the third set to go a double break up," said Djokovic who had led 4-2 in the decider.
The Serb was angry over the playing conditions, made difficult by a sharp shaft of light shooting across the surface while most of the arena was in shade.
"In the end, one side of the court was terrible, almost unplayable," he said.
"I started slowly probably because I played two long matches. But I thought as the match progressed I was feeling okay.
"I was physically fine, we had a lot of exchanges, a lot of rallies. David is playing very quick. You know, he's a fast player.
"I thought I played very, very well for, you know, a set and a half, from the start of the second set. Then, there was that unfortunate game when I dropped my serve, the match turned around. I had my chances, I definitely did. I just didn't use them."
Murray's conqueror Albert Ramos-Vinolas scored his second upset in as many days, stunning fifth seeded Marin Cilic 6-2, 6-7 (5/7), 6-2.
He will next face French 11th seed Lucas Pouille, who beat Uruguay's Pablo Cuevas 6-0, 3-6, 7-5.
Pouille will come into his first Masters 1000 semi-final with a precise game plan.
"Ramos is hitting hard, but he doesn't play fast. He doesn't like to be under pressure," said the Frenchman.
"What I did in the first set today, I will also have to do tomorrow to make it difficult for him. I must not let him dictate from the baseline. I have to be the one dictating the points."
Ramos is also ready.
"I know Pouille, he's a young player coming very strong. It will be super difficult," he said.