Nick Kyrgios of Australia withdrew from his scheduled quarterfinal match against Roger Federer at the BNP Paribas Open on Friday because of illness, tournament officials announced Friday morning.
"We wish him a speedy recovery, and are looking forward to the remaining matches coming up today," a tournament spokesman said in a news release sent via email.
Federer, who won the Australian Open this year to increase his Grand Slam victories to 18, is seeded No. 9 here. He will advance to the semifinals on a walkover and will face the winner of the quarterfinal match Friday afternoon between No. 17 Jack Sock of the U.S. and No. 4 Kei Nishikori of Japan.
Kyrgios, seeded No. 15, had made a strong run to get this far. His serve had not been broken and he had not lost a set. He had won his only previous matchup against Federer, a second-round meeting at the 2015 ATP Masters 1000 Madrid.
"I'm so sorry but I can't play @BNPPARIBASOPEN today," he said on his Twitter feed, adding an emoji of a crying face and another of a face with a thermometer in its mouth. "At this stage we think it's food poisoning, and I'm praying it's nothing more. 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.
"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. I'm sorry to the fans that I'm unable to take to the court but I have to put my health first and I hope you understand. I want to wish Roger the best of luck for the rest of the tournament and thank everyone for their support so far here at the BNP Paribas Open. I will definitely be back. Thank you."
At the end, he inserted another emoji of a crying face.
Federer has a 2-0 career record against Sock, including a victory here in the round of 16 in 2015, and a 5-2 career edge in head-to-head play against Nishikori, including a five-set win in the round of 16 during Federer's push to the Australian Open title.
Federer said he was informed early about Kyrgios' inability to play and offered to visit the stadium, anyway, to conduct TV interviews and to ease the disappointment of fans who hadn't heard about the cancellation of the match. Federer told ESPN he felt bad for Kyrgios and had been intrigued to take on the talented but temperamental 21-year-old Australian.
"That's why I was really excited to play against him. We all know and see Nick's got a big game. I love his first serve and I think he hits the lines at will on either side. And he can move well for a big guy," Federer said. He added that while Kyrgios has enormous potential, Kyrgios must be "willing to put in the work day in and day out."
Speaking to the crowd, Federer repeated that he's still on the comeback from the knee problems that led him to take time off from tournament play after Wimbledon last year.
"Six months off last year was really difficult, I must say. I played one tournament where I felt normal last year and that was the Australian Open. All the other tournaments I was sick, hurt or injured or not well," he said. "So to be back on court feeling normal again is so nice. You feel like you're just happy and fresh and I've tried to show that to the people, and then I've tried to translate that also to my game. I play freely and take chances like I have nothing to lose. And it might be one of the first times in a long, long time that I feel this way.
"I had a blast in Australia and then here again I'm playing great tennis. I didn't expect that, to be quite honest. I still feel like I'm on the comeback but we'll see what the year brings. …I couldn't be more happy and I hope I can keep up this level of play."
Follow Helene Elliott on Twitter @helenenothelen
1:25 p.m.: This article has been updated with reaction from Federer and his records against his potential opponents.