World number one Serena Williams was knocked out of the Wuhan Open in the second round after retiring through illness against France's Alize Cornet.
The top seed, 32, was leading 6-5 in the first set when she received treatment before withdrawing in China.
Cornet, the world number 21, also beat American Williams at Wimbledon and in the Dubai Championships.
Romanian second seed Simona Halep lost 2-6 6-2 6-3 to Spain's world number 22 Garbine Muguruza.
Eleventh seed Sara Errani of Italy was beaten 6-4 6-4 by American Allison Riske, while Russian US Open semi-finalist Ekaterina Makarova, seeded 13, suffered a 6-4 6-1 defeat against Switzerland's Timea Bacsinszky.
Denmark's Caroline Wozniacki, the eighth seed, beat Spain's Carla Suarez Navarro 6-1 3-6 7-6 (7-4).
Meanwhile, British number two James Ward lost 6-4 3-6 7-6 (7-5) to Germany's Philipp Petzschner in the first round of the Malaysian Open.