German ace Tommy Haas stunned world number one Roger Federer in the opening match of the invitational Kooyong Classic on Wednesday. The former world number two rallied back from a one-set deficit to oust the Swiss 3-6, 6-4, 6-4 and give Federer his first defeat of the season. "I struggled for rhythm in the beginning in the first six games or so, but then I broke him twice and won the set and I think he was struggling early on," Federer was quoted as saying by BBC Sport. "I think my last couple of years my first round at Kooyong have always been a struggle and it's always close. I usually have a three-setter but this time I lost," said Federer who won the tournament in 2005. Haas considers the victory as a great boost prior to the Australian Open that begins next week. “I'm very happy with the game," said Haas. "This is definitely a good victory, not only for my own confidence but the game and gives me good hopes to play next week," added the world number 41. Meanwhile, world number three, Andy Roddick topped French teenager Gael Monfils as Guillermo Coria beat Ivan Ljubicic and Nicolas Kiefer defeated Masters Cup champion, David Nalbandian.