Second-seeded Ash Barty is out of the US Open, beaten 6-2, 6-4 by Wang Qiang, who advanced to a Grand Slam quarterfinal for the first time.
The 18th-ranked Wang, who had never been beyond the third round of a major in 20 tries, kept Barty back with consistent groundstrokes that landed deep in the court. She had just 14 unforced errors to her opponent's 39. Barty overcame three match points before Wang finally served out the match, pumping her fist in the air as the Australian's return sailed long.
Barty wasn't the only high seed to go down, however.
No. 16 Johanna Konta knocked off third-seeded Karolina Pliskova 6-7, 6-3, 7-5.
This is the only Grand Slam tournament in which Konta has yet to reach the semifinals. She'll face No. 5 Elina Svitolina, who beat American Madison Keys in straight sets on Sunday night, in the next round.
Barty's loss ends an impressive run of Grand Slam performances this year. She won the French Open, reached the quarterfinals of the Australian Open and the round of 16 of Wimbledon. That record, along with titles at tour events in Miami and Birmingham, England, helped her hold the No. 1 ranking for nearly two months this summer before Naomi Osaka regained the spot.
Wang, the first Chinese woman to get this far in the US Open since Peng Shuai made a run to the semis in 2014, next faces No. 8 Serena Williams, a straight-sets winner over 22nd-seeded Petra Martic.
Information from The Associated Press was used in this report.