Serena Williams has made a stuttering start to her bid to topple Dinara Safina from the world number one spot with an error-strewn 7-5 6-4 win over Estonian Kaia Kanepi in the first round of the China Open .
Safina must at least match Williams's progress over the next week in Beijing to retain the number one ranking and was equally unconvincing in her 6-4 6-4 victory over Italian Roberta Vinci earlier in the day.
Williams missed last week's Pan Pacific Open with knee and toe injuries and looked far from her best in her first singles match since her rant at a lineswoman at the U.S. Open last month.
The fifth seed Caroline Wozniacki of Denmark suffered a first-round upset, crashing out 6-7 7-6 6-0 to Spain's Maria Jose Martinez Sanchez.
Fourth seed Elena Dementiev, had no such problems with her opening match and dispensed with Germany's Anna-Lena Groenefeld 6-4 6-0 in just over an hour.
Dementieva's sixth-seeded fellow Russian Svetlana Kuznetsova started the day by damaging hopes of a first local champion with a 7-6 7-5 defeat of China's number two Zheng Jie.