Serena Williams who lost to clijisters last month regained her number one ranking on tuesday after she defeated Russia’s Ekaterina Makarova in the second round of the China Open on Tuesday. Former world champion Maria Sharapova also defeated Belaueus's Victoria Azarenka to retain her position.Sharapova, who last week won the Toray Pan Pacific in Tokyo for her first tournament victory since returning from a 10-month injury layoff, recovered from a 2-5 deficit in the final set.