Both Roger Federer and Serena Williams were unsuccessful in defending Defending their 2007 titles ; Federer losing Earnings_and_losses to Novak Djokovic in the semi-finals and Williams losing Earnings_and_losses in the quarter-finals to Jelena Jankovic .

1s Victoria Azarenka , Ana Ivanovic , Lleyton Hewitt , Caroline Wozniacki and Jelena Janković .