Petkovic shocks No 1 Wozniacki

World no 1 Caroline Wozniacki suffered a surprise fourth-round defeat to Germany's Andrea Petkovic in the Sony Ericsson Open in Miami yesterday. Petkovic played positive, attacking tennis in the Florida sunshine to move into the quarter-finals with a 7-5, 3-6, 6-3 victory over the Dane. Petkovic saved 12 of 17 break points against Wozniacki but the foundations of her success were an aggressive serve and subtle variations in her game. "Most of the players think they can overpower Caroline. I think that's the wrong approach. What I try to do is mix it up, make her play, and then go for it on the short ball."