Naomi Osaka suffered an upset 3-6 6-3 6-3 defeat against Jil Teichmann on Thursday at the Cincinnati Open.
The world number two took a 6-3 lead in the match but the Swiss came back to win as Osaka struggled with her second serve.
Osaka has played little tennis since withdrawing from this year’s French Open, but said she could “sleep at night” after her efforts in the tournament.
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"I thought that, for me, I felt a bit hesitant, and normally I don't feel that way," she said.
Of course, I put myself in this position by choosing not to play that many tournaments, so, yeah, just feeling more comfortable with it, feeling more confident in myself, as well, because I feel like there were times where I was doubting myself.
"I also thought that my performance in Tokyo was also lingering in my mind a bit because I felt like I was overly aggressive there."
Elsewhere, Olympic gold medal winner Belinda Bencic was 7-5 2-1 up against Karolina Muchova when the Czech player had to retire, giving the Swiss a walkover into the next round.
In the day’s other round of 16 match, Spaniard Paula Badosa secured a 6-2 7-6(7-5) win over Elena Rybakina.

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