Madrid: World No. 1 Amelie Mauresmo was overpowered by fifth-ranked Russian Nadia Petrova 6-2, 6-2 in her opening round-robin match of the WTA championships in Madrid on Tuesday.

Mauresmo, one of three players involved in the battle for the year-end No. 1 spot, had been out of action for 10 days with a shoulder problem and was unable to find the range on her serve.

Although she leads the rankings, the only way Mauresmo can claim the year-end top spot is if she defends her title and rivals Justine Henin-Hardenne and Maria Sharapova slip up badly.

“The shoulder didn’t hurt me, but the lack of play did,” said Mauresmo, who had beaten Petrova in five of their previous seven meetings. “Obviously it can’t get worse and hopefully there is enough time to put things right.”