Tennis: Bad decisions create shock for Wozniacki

World number one Caroline Wozniacki admitted poor decision-making caused her to suffer a shock defeat to Germany's Andrea Petkovic in the fourth round of the Sony Ericsson Open in Miami.

Petkovic, 23, posted an impressive 7-5, 3-6, 6-3 victory over Wozniacki, who landed the Indian Wells title earlier this month.

Seeded 21st, Petkovic toppled the top-ranked Dane in their last-16 clash after imposing a carefully prepared game plan on her opponent.

However, Wozniacki took a philosophical view of the setback, the 20-year-old saying: "I have been playing a lot of matches, but I have been doing so well. (Against Petkovic] I took the wrong decisions?.?.?.?at the important moments. That's what happens sometimes."

Petkovic goes on to face Serbian sixth seed Jelena Jankovic who was a comfortable 6-1, 6-3 winner over Spain's Anabel Medina Garrigues.

Maria Sharapova, seeded 16th, knocked out Australian fourth seed Sam Stosur with a 6-4, 6-1 success in the day's opening match on Stadium court.