Former world No. 1 Roger Federer has pulled out of this week's Madrid Open with a back injury. The Swiss great travelled to the Spanish capital for the tournament but was unable to practice Monday and announced his withdrawal. Federer, however, said he would be back for the Rome Masters next week. "I don't want to take more chances as I know I'm not going to be fully ready for Wednesday," he added, referring to his opening match. "I would rather play it safe and rest up now and get ready for Rome. I'm sorry to the tournament for coming and leaving without playing. "I arrived and I was okay and then I practiced on Saturday and hurt my back a little bit and stopped early. I'm very disappointed to say the least," said Federer. "I changed my schedule around and practiced well in Switzerland before coming here." Federer said he was not worried about his preparations for the French Open that starts on May 22. Women's world No. 5 Victoria Azarenka extended her winning streak to 16 matches with a comfortable 6-3, 6-2 victory over France's Alize Cornet to reach the third round of the Madrid Open Monday. The Belarussian clinched her last two tournaments at Indian Wells and Miami and is the favorite to land her first title in Madrid in the absence of world number one Serena Williams due to flu. Azarenka raced into a 4-1 first set lead against world No. 48 Cornet and, despite a blip dropping serve for the only time in the match for 4-2, broke once more to seal the set 6-3. The second set was even more straight forward for the two-time Grand Slam champion as two breaks of serve sealed victory in just under 90 minutes on court. Azarenka will face either 14th seed Ana Ivanovic or American qualifier Louisa Chirico in the third round. Defending champion Petra Kvitova remained on course for a quarterfinal showdown with Azarenka with a 6-3, 6-3 win over Russian Elena Vesnina. The two-time Wimbledon champion reached the semifinals in Stuttgart a fortnight ago and believes her positive start to the clay-court season is down to her new coach David Kotyza Kvitova faces Australian Daria Gavrilova in round three after she ousted 12th seed Elina Svitolina 6-2, 7-6 (7-4). — Agencies