Naomi Osaka dropped out of the top 10 in the world for the first time since winning the 2018 US Open title on Monday, while taking a break from tennis.
The Japanese star, a former world number one, has not played since leaving the US Open in the third round last month.
Osaka has fallen to 12th in the WTA rankings, her lowest since her first of four Grand Slam titles three years ago at Flushing Meadows, when she defeated Serena Williams in an infamous final.
Last week, the 23-year-old said her return would be “probably soon” and that she has “a little bit” of “that itch” again.
Osaka had previously withdrawn from the French Open and skipped Wimbledon this year to protect her sanity.
Two-time Grand Slam champion Garbine Muguruza jumped to sixth on the standings after winning the title in Chicago last week.
Tunisian Ons Jabeur, who lost to Muguruza in the final, climbed to a career-high ranking of 14th.
WTA top 20 on October 4:
1. Ashleigh Barty (AUS) 9,077 points
2. Aryna Sabalenka (BLR) 7.115
3. Karolina Pliskova (CZE) 5,285
4. Iga Swiatek (POL) 4.756
5. Barbora Krejcikova (CZE) 4.668
6. Garbine Muguruza (ESP) 4,595 (+3)
7. Elina Svitolina (UKR) 4,376 (-1)
8. Sofia Kenin (USA) 4,190
9. Maria Sakkari (GRE) 4.055 (+1)
10. Belinda Bencic (SUI) 3,835 (+2)
11. Petra Kvitova (CZE) 3.735
Naomi Osaka (JPN) 3,326 (-5)
13. Anastasia Pavlyuchenkova (RUS) 3,255
14. Our Jabeur (TUN) 3.220 (+2)
15. Angelique Kerber (GER) 3,105 (-1)
16.Elena Rybakina (KAZ) 2,983 (+1)
17. Simona Halep (ROM) 2,982 (-2)
18. Elise Mertens (BEL) 2,885
19. Cori Gauff (USA) 2,815
20. Anett Kontaveit (EST) 2,616 (+3)
22. Emma Raducanu (GBR) 2.558
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