INDIAN WELLS, Calif. (AP) Jack Sock defeated Kei Nishikori 6-3, 2-6, 6-2 for the biggest singles victory of his career in the BNP Paribas Open quarterfinals on Friday.
The 24-year-old American finally broke through against a top-five ranked opponent after losing his first seven matches against such competition.
Sock improved to 15-2 this year and set up a semifinal against Roger Federer, who advanced via walkover when Nick Kyrgios withdrew with what the Australian suspected was food poisoning.
Sock, the top-ranked U.S. men's player, has already won titles at Auckland and Delray Beach, Florida, this year.
He overcame four match points against 12th-seeded Grigor Dimitrov in the third round and was two points from losing against Malek Jaziri in the third set before he pulled out a 4-6, 7-6 (1), 7-5 fourth-round victory.
Nishikori had not dropped a set in the tournament until losing the first against Sock. The fifth-ranked Japanese had won seven straight matches against American opponents.
Federer got an unexpected day off after Kyrgios withdrew less than two hours before they were to take the court. The Aussie tweeted that he ''had a restless night of being sick.''
He said ''to play a great champion like Roger, I need to be at my best to have a chance.''
Kyrgios' withdrawal spoiled the highly anticipated match with Federer. Neither player had dropped serve in the tournament and their only other meeting was decided in three tiebreakers at Madrid in 2015.
''I was really looking forward to playing the match,'' Federer told fans waiting for the match on stadium court. ''It's a pity.''
Kyrgios beat No. 2 Novak Djokovic in the fourth round, while Federer routed rival Rafael Nadal.
''I'm playing great tennis and I didn't expect it because I'm still on the comeback,'' said Federer, who won his record 18th Grand Slam title at the Australian Open in January after being sidelined by various injuries for much of 2016.
Federer, a four-time winner at Indian Wells, also advanced via a walkover in the quarterfinals in 2008.
Scrambling to find something for fans to watch, tournament officials trotted out tournament director-player Tommy Haas and Vasek Pospisil for a one-set exhibition. Pospisil upset top-ranked Andy Murray in the second round before losing to Dusan Lajovic in his next match.
The women's semifinals later Friday featured No. 14 Elena Vesnina against 28th-seeded Kristina Mladenovic and No. 3 Karolina Pliskova against No. 8 Svetlana Kuznetsova.
Top-ranked Serena Williams withdrew before the tournament began with what she said was a knee injury that will also keep her out of the Miami event next week.