Jessica Pegula became the highest-seeded women's player to lose at Wimbledon, as the No. 5-seeded American was defeated by Wang Xinyu 6-4, 6-7 (7), 6-1 in the second round Thursday.
Wang recorded 38 winners, which combined with 33 unforced errors from Pegula secured the victory and a third-round matchup against Harriet Dart, who beat fellow Briton Katie Boulter in a tense three-set thriller.
For Wang, world No. 42, the victory was her first over a top-10 player.
"Couple of days ago I was asking my coach when will this happen," Wang said. "Jessica was really tough to play on grass. Her ball was super low, and I'm just really happy I won in the end."
For Pegula, the loss ruined high hopes of improving on last year's quarterfinal finish and reaching her first Grand Slam semifinal. She had won her first grass-court title in Berlin in the lead-up to Wimbledon but joined No. 3 Aryna Sabalenka, who pulled out before the first round because of a shoulder injury, on the sideline.
"I would love to say it was good because I won a tournament, but obviously losing second round here isn't ideal," Pegula said about the grass court events this year. "I definitely felt like I was playing better on the grass than I have in the past, but for some reason it didn't really seem to click."
Pegula added that grass has not always been the comfortable surface for her, and the "super windy" conditions didn't help Thursday.
"I still do like it," Pegula said about playing on grass. "I definitely don't have a bad relationship with it. I think it just can be very tricky depending on the day."
No. 1 Iga Swiatek had no such trouble Thursday, winning her 21st straight match and cruising into the third round with a 6-4, 6-3 victory over Petra Martic. No. 4 Elena Rybakina beat Laura Siegemund 6-3, 3-6, 6-3.
Britain's big day got off to a rough start when wild-card entry Yuriko Lily Miyazaki won only 19 points en route to a 6-0, 6-0 loss to Daria Kasatkina. It was the first so-called "double bagel" at Wimbledon this year.
Miyazaki, 28, committed 31 unforced errors and five double-faults in falling to the No. 14-seeded Kasatkina, a Russian who won the Eastbourne title ahead of the grass-court Grand Slam.
Kasatkina will next face Paula Badosa, who advanced Thursday by beating Brenda Fruhvirtova 6-4, 6-2.
No. 12 Madison Keys marked U.S. Independence Day with a 6-2, 6-2 victory over Wang Yafan to reach the third round, as did No. 11 Danielle Collins, who avoided any slip-up in what is likely to be her final Wimbledon with retirement looming. She beat Hungarian qualifier Dalma Galfi 6-3, 6-4 to set up a third-round clash against Brazil's Beatriz Haddad Maia.
"I've always really loved playing during the Fourth of July. I think I've spent more Fourths of Julys in London than anywhere else in the world," Keys said. "It's always fun, and it's definitely an experience. Like today walking by I saw a bunch of Americans, and they all said, 'Happy Fourth.'"
Two-time Wimbledon finalist and No. 10 Ons Jabeur advanced to the third round after a 6-1, 7-5 victory over American teenager Robin Montgomery and will next face No. 21 Elina Svitolina. Russian 17-seed Anna Kalinskaya comfortably beat Czech Marie Bouzkova 6-4, 6-1, and Ukrainian 18-seed Marta Kostyuk produced a fine comeback to beat Australian Daria Saville 4-6, 7-6 (2), 6-4.
The Associated Press and Reuters contributed to this report.