World number one Victoria Azarenka booked her place in the final of the Stuttgart WTA clay-court tournament with a 6-1, 6-3 semi-final win over Agnieszka Radwanska on Saturday. With Azarenka, Maria Sharapova, Petra Kvitova and Radwanska all in Saturday’s semi-finals, this was the first time since Wimbledon in 2009 that the world’s top four players had reached the last four at a WTA tournament. “It’s excellent for women’s tennis to have all of the world’s top four players in the semi-finals,” beamed Azarenka after her victory. This is the fifth time this year Azarenka has beaten Radwanska after seeing off the world number four on hard-court in Sydney, at the Australian Open, in Doha and at Indian Wells. It was the pair’s first meeting on clay, but Azarenka needed just 24 minutes to blitz Radwanska to take the first set as the Polish number one managed just 11 points. In the second set the Belarusian kept up the pressure with an impressive selection of shots. Despite claiming her tenth overall victory over Radwanska in just 77 minutes, Azarenka insisted it had been far from easy. “I think she is such a good player that I have to step up to beat her, I think she brings the best out of my game,” said Azarenka. “We had some good rallies and I was just trying to stay in control of the game.” Despite needing nearly three hours to beat wildcard Mona Barthel in Friday’s quarter-final, Azarenka said she was feeling little fatigue. “Sometimes the long games make you feel tired, but sometimes they energise you and give you confidence,” she said.