American Jack Sock upsets Kei Nishikori to reach semifinals of BNP Paribas Open

American Jack Sock staged one of the biggest upsets of his upward-trending career on Friday when he upset Kei Nishikori of Japan, 6-3, 2-6, 6-2, to reach the semifinals of the BNP Paribas Open at the Indian Wells Tennis Garden.

Sock, a 24-year-old native of Lincoln, Neb., is ranked No. 18 in the world, the top ranking for any American man. On Friday he overcame some tendencies to over-hit the ball and recorded his first-ever victory over a top 5 opponent: Nishikori is ranked No. 5 in the world and was seeded fourth here. Sock is seeded 17th.

Sock’s semifinal opponent on Saturday will be Roger Federer, who advanced on a walkover. Nick Kyrgios, Federer’s scheduled quarterfinal opponent, withdrew from that match Friday morning because of an apparent case of food poisoning.

Sock started off well, breaking Nishikori’s serve in the second game of the first set and clinching the set when Nishikori hit a return wide. But in the second set, Nishikori broke Sock’s serve at love for a 3-1 lead. Nishikori broke serve again to take the second set when Sock hit a wildly long backhand.

But Sock dug in and broke Nishikori’s set in the first game of the third set. Their fifth game was an adventure, with Sock getting four break points before he finally hit a forehand that put Nishikori in a bad position and let Nishikori unable to play the ball. That gave Sock a 4-1 lead, and he went on to finish the match when Nishikori netted a return.

Sock saved four match points in his third-round match here and was two points from being eliminated in his fourth-round match but survived each time. He has won two tournaments so far this season, in Auckland, New Zealand, and at Delray Beach, Fla. His current ranking is the best of his career and it’s sure to improve when the new rankings are issued next week.

In later women’s semifinal matches, No. 28 seed Kristina Mladenovic of France was to face No. 14 Elena Vesnina of Russia, and No. 3 Karolina Pliskova of the Czech Republic was to face No. 8 Svetlana Kuznetsova of Russia. The women’s final will be held on Sunday, as will the men’s finale.