PARIS - In-form Agnieszka Radwanska is up to fourth in the WTA world rankings thanks to her tournament win in Shenzhen. The Polish player moved ahead of Maria Sharapova, who was forced to pull out in Brisbane due to an arm injury. Biggest mover of the week was former Australian Open champion Viktoria Azarenka, who climbed six places to 16th on the back of her impressive win in Brisbane. Serena Williams remained well clear at the top despite skipping the Hopman Cup in Perth because of a knee injury. WTA world top 10: 1. Serena Williams (USA), 2. Simona Halep (ROM), 3. Garbine Muguruza (ESP), 4. Agnieszka Radwanska (POL), 5. Maria Sharapova (RUS), 6. Petra Kvitova (CZE), 7. Angelique Kerber (GER), 8. Flavia Pennetta (ITA), 9. Lucie Safarova (CZE), 10. Venus Williams (USA).