Aryna Sabalenka crashed out of the China Open in the third round following a 6-4 6-3 by Czech Nikola Bartunkova in Beijing on Sunday, the latest setback in a frustrating season for the world number two.
Sabalenka was broken in the opening game and squandered five opportunities to break back in the sixth game of the first set, before going on to lose the match in an hour and 35 minutes.
"I focused on myself, to be calm. Aryna is great. She's a legend. She's a Grand Slam champion," Bartunkova, 20, said.
Four-times major winner Sabalenka has not lifted a trophy since completing the "Sunshine Double" with victories in Indian Wells and Miami earlier this year.
The Belarusian made it to the US Open final last month but was beaten by Elena Rybakina, ensuring she would finish the season without a Grand Slam win for the first time since 2022.
Rybakina replaced Sabalenka at the top of the world rankings after the US Open.
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