Serena Williams of the United States maintained a huge lead atop the women’s tennis rankings issued on Monday by the WTA while German Angelique Kerber has secured the final berth for next week’s eight-player season finale in Istanbul.

Williams, who is already assured of the prestigious year-ending number one ranking, has 13,260 points for a massive advantage over Victoria Azarenka of Belarus (8,206) and injured Russian Maria Sharapova (6,941).

With Sharapova sidelined for the rest of the season, the Istanbul field will be made up of Williams, Azarenka, Agnieszka Radwanska, Li Na, Petra Kvitova, Sara Errani, Jelena Jankovic and Kerber, who qualified by winning the tournament last week in Linz.

WTA top 10 as of October 14 (previous ranking in parenthesis):

1. (1) Serena Williams, United States, 13,260 points

2. (2) Victoria Azarenka, Belarus, 8,206

3. (3) Maria Sharapova, Russia, 6,941

4. (4) Agnieszka Radwanska, Poland, 6,195

5. (5) Li Na, China, 5,365 points

6. (6) Sara Errani, Italy, 4,435

7. (7) Petra Kvitova, Czech Republic, 4,315

8. (8) Jelena Jankovic, Serbia, 3,860

9. (9) Caroline Wozniacki, Denmark, 3,845

10. (10) Angelique Kerber, Germany, 3,805

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