LONDON (AFP) Roger Federer averted one of the biggest shocks in Wimbledon history when the defending mens champion recovered from two sets down to beat Colombias Alejandro Falla in the first round Monday. The Swiss top seed seemed woefully out of form as his unfancied opponent, the world number 60, stunned the crowd by taking the first two sets in the first match on Centre Court this year. But the six-time Wimbledon champion recovered to win 5-7, 4-6, 6-4, 7-6 (7/1), 6-0. Federer, who is chasing a record-equalling seventh Wimbledon mens title, has only lost once at the All England Club since 2002, when he lost the 2008 final to Rafael Nadal. But he avoided becoming only the third ever defending mens Wimbledon champion to lose in the first round by recovering his game. Federer had won all four of his previous encounters with Falla in straight sets, including both of their last two tournaments - two weeks ago on the grass at Halle, and in the French Open. They also met here on Centre Court in the second round in 2004, during Fallas debut at the All England Club, as the Swiss defending champion went on to claim his second Wimbledon title. But despite Federers previous dominance, the Colombian visibly grew in confidence in the first set, which went with serve until 5-5. Falla then created two break points on Federers serve and converted the second with a well-timed volley to stun the Centre Court crowd. The Swiss then went 0-30 up on his opponents serve but Falla dug in and won the set when Federer hit a cross-court forehand out. In the second set, Falla managed to break again for a 4-3 lead. At 5-4, Federer had game point, but he hit the net with a return to take it to deuce. After a string of deuces, in which the advantage swung both ways, Falla eventually triumphed with a drop shot over the net to shock the crowd further by taking a two-set lead. In a key game at 4-4 in the third set, the Colombian had three break points, but Federer pulled it back to deuce. Falla took the advantage but the champion levelled, then held the advantage after a duel at the net, before serving an ace for a 5-4 lead. Federer had a break for set point when Falla hit a shot long, but the Colombian took it to deuce with a superb shot down the line. Federer had the advantage when Falla hit the net, and won the set with a cross-court forehand winner which landed just inside the line to start his comeback. Falla broke on the deuce in the first game of the fourth set to give himself an excellent chance of finishing off his opponent. Federer had a break point at 4-3 down but wasted it, Falla taking the game when Federer sent another mistimed shot looping out. The Swiss held serve to leave the Colombian serving for the match at 5-4 up. Federer took two break points and levelled at 5-5 as Falla fired long, and the Swiss made it 6-5 with an excellent slice over the net - the kind of skilful execution that had hitherto been so badly lacking from his game. In the tie break, Federer broke early and never looked back, taking it 7/1. Federer broke in the first and third games of the fifth set, and finally began to dominate his opponent, eventually showing the form that has made him an all-time Wimbledon great as he at last exerted his superior skill. Meanwhile, Kim Clijsters made up for lost time as she demolished Maria Elena Camerin 6-0, 6-3 in her first singles match at Wimbledon for four years. Clijsters was one of the leading players on the womens tour when she retired in 2007 after becoming disillusioned with her constant battle with injury. But the 27-year-old Belgians fierce competitive instincts couldnt be subdued and, inspired by her participation in an exhibition match at Wimbledon to mark the opening of the Centre Court roof, she decided to dust off her racket last year. It proved an astute choice as, in just her third tournament following her comeback, Clijsters won the 2009 US Open as a wildcard. Now she is back at Wimbledon in her first competitive appearance since losing to compatriot Justine Henin in the 2006 semi-finals. The eighth seed showed she had lost none of her grass-court cunning with a ruthless display against Italys Camerin to set up a second round meeting with Karolina Sprem of Croatia. Clijsters admitted she had suffered a rare case of pre-match nerves but, after an ankle injury sidelined her for several weeks earlier this year, she was just happy to be back on any court let alone one at Wimbledon. I didnt even know if I was going to make it to Wimbledon. So I was relieved I was able to play in Eastbourne (last week), she said. There were definitely times where I was like, 'Oh, man, here we go again with these injuries. It was frustrating. I thought, 'Was this all worth it? I was actually pretty nervous, leaving the locker room and going out on court here again. To be on the new Court Number Two was interesting. I had to find my way to get there a little bit. Luckily the security guard knew where we were going, because I actually had no idea But it was nice. I was excited to be out there again. Overall I played a good match. I know that if I play my best tennis I can definitely compete with the top players here. She was on top right from the start and quickly broke to underline her superiority. Camerin had no answer as Clijsters took the first set without losing a single game. The second set was tighter as Camerin finally showed more steel on her own service games. But Clijsters had too much quality to be kept at bay for long and the former French and Australian Open finalist broke for a 5-3 lead before serving out the match.