No. 2 seed Naomi Osaka made a first-round exit from Wimbledon, losing to unseeded Yulia Putintseva of Kazakhstan in straight sets on Monday.
Putintseva, the No. 39-ranked player in the world, topped No. 2 Osaka 7-6, 6-2 on a day of notable upsets.
Osaka had risen to No. 1 in the world after consecutive major titles at last year's U.S. Open and the Australian Open in January. Later in the day, seven-time major champion Venus Williams lost in straight sets to teenager Cori "Coco" Gauff, 6-4, 6-4.
American Madison Brengle upset No. 16 seed Marketa Vondrousova of the Czech Republic 6-4, 6-4, while Slovakia's Magdalena Rybarikova beat No. 10 seed Aryna Sabalenka from Belarus 6-2, 6-4 and No. 29 seed Daria Kasatkina of Russia lost 6-3, 6-1 to Croatia's Ajla Tomljanovic.
Osaka, who came into the match 0-2 against Putintseva, was considered to have a tough draw. The most recent win by Putintseva came 10 days ago at the Nature Valley Classic in Birmingham, England.
Since winning the Australian Open in January, Osaka's best showing in nine tournaments was making the semifinals in Stuttgart.
Asked in her post-match press conference if she has found it difficult to get used to her new level of fame as a global superstar, Osaka, still in her match outfit, asked if she could stop the press conference.
"I feel like I'm about to cry," she told the media relations representative before getting up and leaving the room.
"I'm sorry, you'll have to leave that there," the representative told the media.
Meanwhile, Williams entered the tournament ranked No. 44 and knew she was in for a tough battle. The 15-year-old Gauff has been a rising star on the junior circuit. The Atlanta native who lives in Florida and has trained in France, became the youngest player to qualify for Wimbledon in the Open Era by winning her third qualifying round.
Gauff showed few signs of nerves against five-time Wimbledon champion Williams, one of her idols growing up. Gauff was never broken, holding off a break point in the final game before closing it out to become the youngest woman to win a Wimbledon match since Jennifer Capriati in 1991 (14 years, 90 days).
"Honestly, I don't really know how to feel," Gauff told ESPN after the match. "This was the first time I ever cried after a match -- or winning, of course. I don't even know how to explain how I feel.
"I definitely had to tell myself to stay calm. I've never played on a court so big. I had to remind myself that the lines on the court are the same size. Everything around it might be bigger, but the lines are the same. And I was just telling myself after every point to stay calm."
Gauff received words of encouragement at the net from the five-time Wimbledon champion.
"She just told me congratulations, and to keep going," Gauff said. "I told her thank you for everything she did. I wouldn't be here if it wasn't for her. And I was just telling her that she's so inspiring. I always wanted to tell her that ... and even though I've met her before, now I just had the guts to."
Gauff will play Rybarikova in the second round.
"I never thought this would happen," Gauff said of reaching the second round. "I'm literally living my dream right now. Not many people get to say that, so I'm just happy that Wimbledon gave me the opportunity just to play. And I never thought that I'd be this far."
Williams, 39, responded "that's the plan" when asked if she'll be back at Wimbledon next year and said of Gauff: "She played so well, even all the shaped balls went in. I actually didn't play well, so it was a contrast of both sides."
Among the higher seeds to advance were No. 3 Karolina Pliskova of the Czech Republic, No. 7 Simona Halep of Romania and No. 8 Elina Svitolina of Ukraine.
Pliskova had to fight off China's Lin Zhu to complete a 6-2, 7-6 (4) victory, Halep defeated Aliaksandra Sasnovich of Belarus 6-4, 7-5 and Svitolina posted a 7-5, 6-0 win over Australia's Daria Gavrilova.
Also, No. 17 seed Madison Keys rolled to a 6-3, 6-2 win over Thailand's Luksika Kumkhum, and No. 27 Sofia Kenin cruised to a 6-4, 6-2 victory over Australia's Astra Sharma.
--Field Level Media