Paris - US and Australian Open champion Naomi Osaka returned to the world No 1 spot in the WTA Tour rankings on Monday.

The 21-year-old lost to Serena Williams in the quarter-finals of last week's Rogers Cup but benefitted from the second round defeat of former number one Ashleigh Barty and the failure of Karolina Pliskova to reach the semis in Toronto.

Osaka first hit top spot in January, after winning back-to-back majors in New York and Melbourne, making history as the first Japanese player to achieve it.

After seven weeks on top, Barty slips to second with Pliskova in third.

The only other movement in the top 10 sees Williams, finalist in Toronto, climbing two places to eight with Sloane Stephens going in the other direction.

Canadian Bianca Andreescu, who won the Rogers Cup following Williams' withdrawal with back spasms in the opening set of the final, climbs 13 places to 14.

Top 20 in the latest WTA Tour rankings:

1. Naomi Osaka (JPN) 6,417 pts

2. Ashleigh Barty (AUS) 6,256

3. Karolina Pliskova (CZE) 6,185

4. Simona Halep (ROU) 5,223

5. Kiki Bertens (NED) 5,120

6. Petra Kvitova (CZE) 4,780

7. Elina Svitolina (UKR) 4,577

8. Serena Williams (USA) 3,995

9. Aryna Sabalenka (BLR) 3,565

10. Sloane Stephens (USA) 3,189

11. Anastasija Sevastova (LAT) 3,167

12. Belinda Bencic (SUI) 3,008

13. Angelique Kerber (GER) 2,875

14. Bianca Andreescu (CAN) 2,837

15. Johanna Konta (GBR) 2,695

16. Marketa Vondrousova (CZE) 2,652

17. Qiang Wang (CHN) 2,647

18. Madison Keys (USA) 2,557

19. Caroline Wozniacki (DEN) 2,537

20. Anett Kontaveit (EST) 2,380

Others:

40. Victoria Azarenka

65. Venus Williams

97. Maria Sharapova