LONDON (AFP) - Defending champion Serena Williams, who described her recent struggles against life-threatening blood clots as like being on her death bed, broke down in tears on Tuesday on her Wimbledon return. The four-time winner, watched by US pop superstar Diana Ross and England's Ashes-winning cricketers in the Royal Box, battled past Frenchwoman Aravane Rezai 6-3, 3-6, 6-1 in what was only her third match in 11 months. "To be able to come back at Wimbledon is pretty awesome, I didn't expect to play or do anything. I'm just excited." While Williams, who next tackles Romania's Simona Halep, was wiping away tears, six-time men's champion Roger Federer barely broke sweat in clinching a 7-6 (7/2), 6-4, 6-2 win over Mikhail Kukushkin of Kazakhstan. Third-seeded Federer, who next faces either Ireland's Conor Niland or France's Adrian Mannarino, suffered a shock quarter-final exit against Tomas Berdych last year, but never looked in trouble against tournament debutant Kuskushkin. The Swiss star fired down 12 aces and unleashed 53 winners in his quick fire Centre Court win. "It was very windy and the conditions were tough," said Federer, the holder of a record 16 Grand Slam titles. "It's always nerve-wracking playing your first match on Centre Court because you don't get the chance to practice at the start of the tournament. But it was a matter of playing solid." Three-time finalist Andy Roddick eased into the second round with a 6-4, 7-6 (8/6), 6-3 over German qualifier Andreas Beck, while former US Open winner Juan Martin del Potro beat Flavio Cipolla 6-1, 6-4, 6-3. On a day when 95 singles matches were due to be played because of Monday's torrential downpours, second seed Novak Djokovic, playing for the first time since Federer ended his 43-match winning run at the French Open, begins against Jeremy Chardy of France. Women's world number one Caroline Wozniacki raced into the second round as she routed Spain's Arantxa Parra Santonja 6-2, 6-1, taking just 59 minutes to demolish the world number 105. "It was my first match on grass and the wind was blowing everywhere. The conditions were pretty tough," Wozniacki said. Former world number one Jelena Jankovic, the 15th seed, slumped to a first round loss, going down to Spanish left-hander Maria Jose Martinez 5-7, 6-4, 6-3.