Dinara Safina finished the best year of her career with tears in her eyes yesterday, as a serious back injury ended her season and her hold on the No. 1 ranking she owned for much of 2009.

Safina lasted just 13 minutes in her first round-robin match of the Sony Ericsson Championships before calling it quits while serving at 1-1 against Jelena Jankovic.

Her withdrawal meant she lost the year-end No. 1 ranking to Serena Williams, a sour ending to a season that saw her become firmly established as one of the sport's top stars.

"I did everything possible to play here," Safina said. "As I was chasing this No. 1 (ranking), I was fighting with my body."

After stopping play in the third game, a teary-eyed Safina walked over to her chair and covered her face with a towel before retiring.

She said one of the discs in her lower back was "starting to fracture" and that she has been dealing with the pain for three months.

"Maybe I had to stop after the US Open. But then for two tournaments, let's say Beijing and Tokyo, it was quiet, it didn't bother me that much," she said. "But then my body just gave up."

Rehabilitation

Now she faces six weeks of rest before stepping back on the court, and a potentially long rehabilitation process.

In fact, she is worried she might not be fit enough to play in the Australian Open in late January.

"When I speak with the doctors, it doesn't sound so good," Safina said. "It is possible I may have to skip it."