Dinara Safina has pulled out of the Sony Ericsson Championships with a serious back injury, handing the year-end No. 1 ranking to Serena Williams.
Safina was serving at 1-1 in the first set against Jelena Jankovic Wednesday when she had to retire.
She said her back has been hurting for three months and that she took cortisone injections to be able to defend her No. 1 ranking in Doha. Safina said doctors told her she will be sidelined for at least six weeks and may not be fit in time for next year's Australian Open.
Safina regained the top ranking this week, but her margin over Williams is so slim that the player who performed best in Doha was guaranteed to end the year as No. 1. Williams won her first match Tuesday.