Indian Well - Australian star Nick Kyrgios withdrew from his Indian Wells Masters quarter-final showdown with Roger Federer on Friday, blaming food poisoning for a sudden illness.
"Unfortunately I am unable to play today due to sickness," Kyrgios said on Twitter. "At this stage we think it's food poisoning, and I'm praying it's nothing more."
Kyrgios had been due to face Federer after knocking out Novak Djokovic in the last 16 on Wednesday.
Kyrgios's illness is a cruel twist of fate for the talented 21-year-old, who has shown signs of finally starting to deliver on his promise in recent weeks after a young career marked by controversy.
His stylish win over Djokovic was the second time in as many weeks he had beaten the former world number one after also defeating the Serb in Acapulco.
In his statement on Friday, the world number 16 said he had taken the decision to pull out in California with a heavy heart.
"After a restless night of being sick I have nothing left and to play a great champion like Roger I need to be at my best to have a chance," Kyrgios said.
"I don't take this decision lightly, these are the matches we train for, but I'm in no fit state to take to the court," he added.
"I'm sorry to the fans... but I have to put my health first and I hope you understand."
Federer, meanwhile, tweeted his support to the Australian youngster.
"Hope you feel better @NickKyrgios," said the Swiss ace, who will face either fourth-seeded Kei Nishikori of Japan or 17th-seeded Jack Sock of the United States.
Federer, who seized his 18th Grand Slam title at the Australian Open in January after a 2016 campaign disrupted by injury, took the court briefly Friday to speak to disappointed fans.
"I was actually really looking forward to the match," said Federer, who had looked sharp in a 6-2 6-3 dismantling of Rafael Nadal in the fourth round - a reprise of his thrilling five-set victory over his old foe in the final in Melbourne.
"I think the six months off last year was really difficult," Federer said. "I played one tournament where I felt normal. All the other tournaments either I was sick, hurt or injured.
"To be back on court feeling normal again is so nice, you feel just happy and fresh and I think it translates also to my game. I can play freely, take chances like I have nothing to lose - it might be one of the first times in a long, long time I feel this way."