World number two Anett Kontaveit is out of the Western and Southern Open in Cincinnati, Ohio, after losing to Zhang Shuai (PRC), 2:6, 6:4, 6:4.
The encounter on the outdoor hard courts at the Lindner Family Tennis Center on Thursday was the fifth between Kontaveit, who went out of the women's doubles earlier in the week, and Shuai, while the record was 3:1 in the Estonian's favor, going in to Thursday.
Kontaveit had won their last encounter in Sydney in January, in straight sets and without dropping a service game.
Thursday's match at first looked like it might be business as usual as Kontaveit raced to a 4:0 lead, breaking Shuai's serve twice.
While Shuai, ranked 44th in the world, immediately returned the favor by breaking Kontaveit's serve, she only had the chance to win one more game off her service before the Estonian came out on top 6:2.
In set two, things were more even, with Kontaveit heading off a service break in game two, but Shuai played well and went on to win 6:4.
In the decider, Kontaveit went 4:2 up and looked like all was not lost, only for Shuai to win four games in-a-row and take the set with no answer from the Estonian.
Shuai players either Belarusian player Arina Sabalenka or Shelby Rogers of the U.S. in the next round.
The U.S. Open starts on August 29.
Editor: Andrew Whyte