 Complete the following phrase:  Petkovic made her comeback in a Fed Cup match in April, losing to Samantha Stosur. She then played at the Porsche Tennis Grand Prix in Stuttgart, beating Kristina Barrois in the first round. In her second round match against Victoria Azarenka, Petkovic was down 26 and 44 when she rolled her right ankle. She was forced out with what was later revealed to be torn ankle ligaments, which required surgery and kept her out for another four months, including the French Open, Wimbledon, and the 