Wuhan - World No 2 Simona Halep was dumped out of the Wuhan Open 6-2, 6-1 by Russia's Daria Kasatkina on Tuesday, becoming the ninth seed to tumble at the tournament.
Halep, seeded two, begun the second-round match strongly and immediately broke her opponent. But she was later let down by her service game, managing to convert just 12 percent of her second serves.
The 25-year-old Romanian was competing in her first match since the opening round of the US Open, where she crashed out to Maria Sharapova.
"I didn't play for a month. It's tough to come back and to play matches... Maybe it was a mistake that I didn't play, but I needed rest after the US season," she said after the match.
"What I saw after the US Open was that my serve is too soft for the big players, so that's why I decided to work on it more," she added.
In other matches, Karolina Pliskova triumphed over China's second-ranked player Zhang Shuai after a tense three-set battle.
The 25-year-old Czech overpowered Zhang 6-4, 3-6, 6-4 in just over two hours, breaking an unlucky streak for the competition's top seeds that has seen nine exit the Chinese tournament over the first two days.
Pliskova, seeded three, has never lost a match against Zhang and once again showed she had the measure of her Chinese opponent, who had been on a high after winning the Guangzhou Open last week.
She will now face another home crowd favourite, Wang Qiang, the first-ever Chinese player to reach the third round at Wuhan.
Elsewhere, Latvian Jelena Ostapenko, seeded eight, triumphed over Czech player Barbora Strycova 2-6, 7-5, 6-3.
Agnieszka Radwanska, seeded nine, defeated German Julia Gorges 7-5, 7-5.
Johanna Konta, Sloane Stephens, Madison Keys and Petra Kvitova were among the top seeds to exit the tournament on Monday.