The Japanese lost to 20th placed Sofia Kenin in the quarter-finals on Sunday due to a knee injury. Her participation at the US Open is still uncertain.

Madison Keys jumped eight spots and is ranked 10th after she won Cincinnati on Sunday.

Also on the rise in an otherwise unchanged top 10 is Elina Svitolina who moved up two spots to fifth, a career high for Ukrainian.

Sloane Stephens was robbed of her 10th spot in the rankings and sits at 11th after her defeat to Svetlana Kuznetsova in Cincinatti's third round.

Meanwhile, Kiki Bertens took two steps back to 7th place and Johanna Konta was demoted to 16th.

WTA Rankings, August 19:

1. Naomi Osaka (JPN) 6,606 pts
2. Ashleigh Barty (AUS) 6,501
3. Karolína Plísková (CZE) 6,315
4. Simona Halep (ROU) 4,743
5. Elina Svitolina (UKR) 4,492 (+2)
6. Petra Kvitová (CZE) 4,485
7. Kiki Bertens (NED) 4,325 (-2)
8. Serena Williams (USA) 3,935
9. Aryna Sabalenka (BLR) 3,320
10. Madison Keys (USA) 3,267 (+8)
11. Sloane Stephens (USA) 3,189 (-1)
12. Anastasija Sevastova (LAT) 3,167 (-1)
13. Belinda Bencic (SUI) 3,008 (-1)
14. Angelique Kerber (GER) 2,870 (-1)