Petrova next headed to 2009 MPS Group Championships as the top seed, where she defeated Olga Govortsova, Madison Keys (who had just won her first main-draw match), and Alona Bondarenko. She fell in the semifinals to eventual finalist Aleksandra Wozniak, 4-6, 6-4, 2-6. Petrova fell in the second round at 2009 Family Circle Cup to Melinda Czink, 6-3, 4-6, 5-7. At the 2009 Porsche Tennis Grand Prix, Petrova was seeded sixth, but lost in the second round to Flavia Pennetta, 2-6, 2-6. She next went to the Rome Masters as eighth seed, where she had a first-round bye before defeating giant-killer Carla Suarez Navarro. In the third round, Petrova was ousted by Maria Jose Martinez Sanchez, 4-6, 7-6(5), 4-6.

Answer this question based on the article: How many sets did Aleksandra Wozniak beat Petrova by six points?
2