Sept. 3 (UPI) -- Defending champion Naomi Osaka was ousted in the third round of the U.S. Open tennis tournament after a stunning loss to unseeded Canadian teen Leylah Fernandez on Friday in Flushing, N.Y.
Osaka suffered a 5-7, 7-6 (2), 6-4 loss to the 18-year-old Fernandez, who is ranked 73rd and had never advanced this far in a Grand Slam event. The defeat snapped Osaka's 16-match winning streak at major tournaments.
This was Osaka's first Grand Slam event since she withdrew from the French Open before the second round to take a mental health break. She then sat out Wimbledon before competing at this summer's Tokyo Olympics.
Osaka pulled away for a straight-sets win over Marie Bouzkova in the first round earlier this week, but she hadn't competed since that win Monday due to her second-round opponent, Olga Danilovic, withdrawing due to an illness.
Trying to shake off the rust from that extended layoff, Osaka grabbed 12 of the last 13 points -- including the last nine -- with a break at love to take a 6-5 lead in the opening set, later using a pair of aces at 112 mph and 114 mph to win the set.
Osaka was on track for a similar outcome in the second set, holding a 6-5 lead and serving. But after she sailed a forehand wide, Fernandez had her first break of the match to make it 6-all.
From that point onward, Osaka unraveled and lost her composure inside Arthur Ashe Stadium. She fell behind 5-0 in the ensuing tiebreaker and continually showed her frustration by throwing her racket. Chair umpire Alison Hughes didn't sanction Osaka, though a warning was issued later after Osaka hit a ball into the stands.
"Honestly, I wasn't focusing on Naomi," Fernandez said. "I was only focusing on myself and what I needed to do."
Fernandez took control of the match with the help of her serve. She won 18 of 19 first-serve points -- and never faced a break point -- in the decisive third set.
Next up, Fernandez will challenge three-time Grand Slam champion Angelique Kerber, who won the 2016 U.S. Open. Kerber defeated unseeded Sloane Stephens in the third round to advance.
Also Friday, No. 5 seed Elina Svitolina, No. 8 Barbora Krejcikova, No. 9 Garbine Muguruza, No. 12 Simona Halep and No. 15 Elise Mertens reached the fourth round.
On the men's side at the U.S. Open, second-seeded Daniil Medvedev cruised to a straight-sets victory over unseeded Pablo Andujar in the third round.
No. 3 seed Stefanos Tsitsipas, however, suffered a shocking loss in five sets to unseeded Spaniard Carlos Alcaraz.
No. 11 Diego Schwartzman, No. 12 Felix Auger-Aliassime and No. 24 Daniel Evans also reached the fourth round in New York.