Cincinnati Open first round loss

Osaka beaten in first round again

It was only her third tournament back from an Achilles injury and it has been a stuttering return to action for the twice U.S. Open champion, who also exited in the opening round in Toronto last week, retiring with lower back pain.

For Zhang, doubles champion in Cincinnati last year, it was her first singles win at the event since 2014.

"Naomi she is amazing but I don't know she is maybe not really feeling good today," said Zhang. "But for sure today - not her best today."