DOHA: Dinara Safina faces a desperate Australian Open fitness battle after suffering a crippling back injury at the WTA Championships which also forced her to tearfully surrender her world number one ranking.

The 23-year-old Russian, who said she had been plagued by inflammation in her lower back for over three months, lasted just two games and 13 minutes in her tournament opener against Jelena Jankovic on Wednesday.

Her failure to win a match here means that bitter rival Serena Williams will now claim the widely-coveted year-end top spot which she had also clinched in 2002.

As well as her battered body and bruised pride, Safina admits that the rehabilitation programme she now faces could rule her out of the Australian Open in January, the first Grand Slam event of 2010.

"It's a question if I will be able to play in Australia, because when we speak with the doctors, it doesn't sound so good. So it's possible that I might even not be 100-percent fit for the Australian. Maybe I'll have to skip it," said Safina.

The Russian had regained the top spot in the rankings from Williams on Monday, having already spent 25 weeks as world number one earlier in the season.

But her lofty place had come under widespread fire due to her glaring absence of a Grand Slam title compared to Williams's collection of 11.

Safina was the runner-up to Williams at the Australian Open in 2009 and consequently has a huge number of points to defend in Melbourne.

"It's going to be disappointing (if she had to skip the Australian Open). But, at this stage, health is more important," she said.

"If my back is not healthy, what can I do? I can go to Australia, play two games and I can shake hands. If I'm not fully recovered, I'll not play."

Safina said she needed a cortisone injection in order to make the 4.55 million dollar WTA Championships, a tournament where she lost all three matches on her debut in 2008.

But she refused to blame the gruelling demands of the WTA schedule.

"We make the schedule, so all the injuries are on us. I wouldn't complain about it because if I lose everywhere in the first round, I wouldn't have this problem."

She had started feeling the pain on her way to her third title of 2009 in Portoroz in July, but had been determined to keep playing to stay on course for the world number one spot.

"I have been on anti-inflammatories, on everything, but my body just gave up," said the Russian, who arrived in Doha with a slender 155-point lead on Williams in the rankings.

The American erased that deficit with a win over Svetlana Kuznetsova on Tuesday.

"I was advised to take a break after the US Open. But I thought that I was chasing this No. 1 place, I was fighting with my body.

"God knows, maybe I should have stopped after the US Open. But for two tournaments - in Beijing and Tokyo - it didn't bother me that much. So I was still hoping."