Jack Sock jolts Kei Nishikori, advances to semis at Indian Wells

American Jack Sock recorded the biggest victory of his career on Friday when he beat fourth-seeded Kei Nishikori 6-3, 2-6, 6-2 in the quarterfinals of BNP Paribas Open on Friday in Indian Wells, Calif.

Sock secured his first career win over a top-five player when he finished off the third set against Nishikori, who is ranked No. 5. Sock's semifinal opponent will be Roger Federer, who advanced with a walkover after Nick Kyrgios withdrew with an illness.

"Honestly, you never know when (that big win) is going to come," Sock said, according to SI.com. "You can be feeling good and playing well and the other guy could be playing better that day and that's that. I made a lot of improvements, I have a lot of confidence right now in my game and in my body right now, and I feel like I can compete with a lot of the guys. Today it just went my way."

Sock improved his match record to 15-2 this year, and he is looking to improve his career-high ranking of No. 18 achieved this week. He has already won titles this year at Auckland, New Zealand and Delray Beach, Fla.

Sock overcame four match points to beat 12th-seeded Grigor Dimitrov in the third round and was two points from losing against Malek Jaziri in the third set before winning that fourth-round match, 4-6, 7-6 (1), 7-5.

Nishikori had not dropped a set in the tournament until Friday.

Nishikori won the second set, but Sock broke his foe's serve in the first game of the third and jumped out to a 2-0 lead. Sock broke Nishikori's serve again in the 16-point fifth game to take a 4-1 lead. Sock held his serve in a long sixth game to take a 5-1 lead, then finished things off by converting his first match-point opportunity.

"For sure he served really well," Nishikori said. "I usually am able to return and get more chance on my return game. But today I think there was almost no break points for me. Also, he gets a lot of balls back. He has great footwork. He has big forehand. He played really good today."

Federer did not have to play to win his quarterfinal match.

"Unfortunately, I am unable to play today due to sickness," Kyrgios said in a statement. "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."

Kyrgios eliminated defending champion Novak Djokovic in the fourth round, while Federer dismissed Rafael Nadal in straight sets.

"Hope you feel better @NickKyrgios," Federer tweeted.