Women singles\' world number two Victoria Azarenka has withdrawn from the second-round match and pulled out of the 2013 Wimbledon Championships with a knee injury on Wednesday. Azarenka, who had been scheduled to face Italy\'s Flavia Pennetta in the first match of the day on Centre Court, didn\'t appear at Wimbledon\'s biggest stage, where the second-round match between No.12 seed Ana Ivanovic and Eugenie Bouchard thus was moved in. The 23-year-old of Belarus, who has reached the semi-finals in her past two visits to Wimbledon, fell awkwardly early in the second set of her first round match against Maria Joao Koehler of Portugal on Monday. She cried and creamed in pain, then received treatment and required heavy strapping to continue the match, which she won at 6-1, 6-2. It proved the injury too serious to recover from in time to play on Wednesday, handing Pennetta a pass into the third round where she will meet Alize Cornet of France. Elsewhere, it proved an unlucky morning for some players. According to the official website of Wimbledon, no fewer than four players pulled out of the Championships, including Rafael Nadal\'s first-round conqueror, Steve Darcis. Darcis did not even make it onto court to play his second-round match against Lukasz Kubot because of a shoulder injury. John Isner, who tweaked his left knee in the opening game against France\'s Adrian Mannarino, could only complete one more game before retiring with the score 1-1. Within minutes, at another court, Radek Stepanek realised he would not be able to shake off a thigh problem and he retired against Jerzy Janowicz while trailing 6-2, 5-3. From: XINHUA