Seven-times grand slam winner Venus Williams retired injured during her third round match against German 30th-seed Andrea Petkovic at the Australian Open in Melbourne on Friday.
Williams strained a muscle in her lower body during her second-round match against Czech Sandra Zahlavova on Wednesday and the number four seeded American pulled out after losing the first game of the match.
Maria Sharapova strained her vocal chords to exhaustion as the 2008 champion fought off a stiff challenge from another German, Julia Goerges, to advance to the fourth round 4-6 6-4 6-4.
Another Russian, Svetlana Kuznetsova, ended the run of Belgium's Justine Henin 6-4 7-6(8).
Chinese ninth seed Li Na progressed as did Italian sixth seed Francesca Schiavone, while top seed Caroline Wozniacki of Denmark opened proceedings on Rod Laver Arena with a straight sets win over Slovakia's Dominika Cibulkova.
