Denmark's Caroline Wozniacki will end the year as world number one for the second season running despite losing to Vera Zvonareva at the WTA Championship.
Wozniacki lost 6-2 4-6 6-3 but secured the top ranking as nearest rival Maria Sharapova pulled out with an ankle injury after losing 7-6 6-4 to Li Na.
"It's amazing for me to finish the year as number one once more," said Wozniacki.
Sam Stosur, who beat Sharapova in her first match, lost to Victoria Azarenka.
Sharapova, who will be replaced in the elite eight-player field by France's Marion Bartoli, said: "It just limits my movement a lot, and it's not something I really want to risk.
The Russian, who was playing her first tournament since suffering the ankle injury in Tokyo, added: "I have no regrets. I definitely progressed from last year and I've improved, and my game has stepped up.
"I still feel like going into next year there's so many things that I can improve that can make me better. It's just something I look forward to when I start training again."
In the final match of the day, Zvonareva, who had lost the previous two meetings against Wozniacki, broke the Dane's serve twice in the opening four games to lead 4-0 before clinching the first set in just 34 minutes.
In the second set, the games went with serve until the 10th when the 21-year-old Wozniacki broke the Russian's serve for the first time to take the set.
Zvonareva, who beat Wozniacki earlier this year in the final of the Qatar Open, then took a 4-1 lead in the third before closing out the match.
With one win and one loss in the Red Group, Wozniacki could still miss out on the semi-finals of the season-ending event even if she beats Wimbledon champion Petra Kvitova on Thursday.
And asked again about her number one status, in the light of her lack of a Grand Slam title, she added: "I think people do realise the true importance of it.
"If you ask any little girl or any little boy, everyone will know what it means to be number one. Maybe not everyone will understand what a Grand Slam is, because you have to be into tennis to know that. If you're number one it means you've done something remarkable."
Earlier, Sharapova raced to a 4-1 lead over Li before her Chinese opponent levelled at 4-4.
The match went with serve for the remaining four games and despite Sharapova making 72% of her first serves in the opening set, she collapsed from 4-0 up in the tie break to lose 7-4.
Li powered to a 5-2 advantage in the second and the world number five managed to hold her nerve on match point to take the win.
Belarusian world number four Azarenka strolled to a 6-2 6-2 win over US Open champion Stosur in just one hour and 18 minutes.
However, Stosur, the world number seven, can still qualify for the semi-finals if she beats Li in her last round-robin match.