BERLIN: World number one Naomi Osaka made a winning start to her claycourt season by beating Taiwan’s Hsieh Su-wei 6-4 6-3 on Thursday to move into the quarter-finals of the Porsche Tennis Grand Prix. The twice grand slam champion, who has yet to win a title on clay, found little resistance as she avenged her defeat to Hsieh in Miami last month. A break was enough for Osaka to win the first set as she looked somewhat uncomfortable on Stuttgart’s quick indoor clay, designed to be similar to next month’s French Open courts. There was nothing wrong with her serve, however, as she fired seven aces during the contest. After going 2-0 up in the second set, Osaka grew in confidence and broke again to seal her first win on clay this season on her first match point. Victory also meant she will hold on to her world number one ranking after this week. Osaka will next face Croatia’s Donna Vekic who beat Daria Kasatkina 6-1 7-5. Former world number one Victoria Azarenka of Belarus will take on fourth seed and defending champion Karolina Pliskova for a spot in the quarter-finals later on Thursday.