Serena Williams has dropped out of the world's top 50 for the first time since 2006, the US tennis great sitting 59th in the WTA rankings released on Monday.

The 40-year-old played just six tournaments in 2021 and none since her tearful Wimbledon first-round exit with a leg injury ended the 23-time Grand Slam champion's latest bid to equal Margaret Court's all-time record.

Williams has dropped 12 places in the rankings which are led by Ashleigh Barty ahead of the Australian Open in Melbourne.

Sydney winner Paula Badosa moves up to a career-high sixth following a blistering 2021 season in which she reached the French Open quarter-finals, the 24-year-old Spaniard having started last year ranked 67th.

American Madison Keys, a former world number seven, has jumped 36 places to 51st after her Adelaide victory, claiming a WTA title more than two and a half years after her last tournament win in Cincinnati.

WTA top 20

1. Ashleigh Barty (AUS) 7,111 pts

2. Aryna Sabalenka (BLR) 5,698

3. Garbine Muguruza (ESP) 5425

4. Barbora Krejcikova (CZE) 5,213

5. Karolina Pliskova (CZE) 4,582

6. Paula Badosa (ESP) 4,264 (+3)

7. Anett Kontaveit (EST) 4,231

8. Maria Sakkari (GRE) 4,071 (-2)

9. Iga Swiatek (POL) 3,916 (-1)

10. Ons Jabeur (TUN) 3,500

11. Anastasia Pavlyuchenkova (RUS) 2,968

12. Elena Rybakina (KAZ) 2,765 (+1)

13. Sofia Kenin (USA) 2,762 (-1)

14. Naomi Osaka (JPN) 2,696

15. Simona Halep (ROM) 2,657

16. Cori Gauff (USA) 2,655 (+3)

17. Elina Svitolina (UKR) 2,641 (-1)

18. Emma Raducanu (GBR) 2,595

19. Petra Kvitova (CZE) 2,530 (+2)

20. Angelique Kerber (GER) 2,517 (-3)

Selected:

51. Madison Keys (USA) 1,153 (+36)

59. Serena Williams (USA) 1,061 (-12)