World number one Osaka retires from Cincinnati quarter-final with injury

World number one Naomi Osaka retired from the Cincinnati Masters with an apparent knee injury on Friday less than two weeks before the start of her U.S. Open title defence. Osaka was trailing American Sofia Kenin in the third set of their quarter-final in Cincinnati when she sought treatment on her left knee.

After briefly returning to play, Osaka retired with Kenin leading 6-4 1-6 2-0. The Japanese star's withdrawal leaves both of the 2018 U.S. Open finalists having retired from the tournament. American Serena Williams withdrew with back problems after also pulling out from the final of the previous week's Rogers Cup with similar problems.