Naomi Osaka lost to former French Open finalist Markéta Vondroušová of the Czech Republic 6-1, 6-4 in the third round of the Tokyo tennis tournament Tuesday.
The second-ranked Osaka, who was born in Japan and grew up in the United States, struggled with her usually reliable groundstrokes.
The 42nd-ranked Vondrousova produced a series of drop-shot winners and other crafty shots that drew Osaka out of her comfort zone.
Osaka won her opening two matches in straight sets following a two-month mental-health break. But conditions were different Tuesday with the roof closed because it was raining outside.