US Open champion Samantha Stosur insists she is still on track for a successful Australian Open despite being stunned in the second round of the Brisbane International on Wednesday. Iveta Benesova ensured Stosur's miserable run at her home tournament went on when the unseeded Czech defeated the top-seeded Stosur 6-4, 6-2 at the Pat Rafter Arena. The tournament could also be set to lose the fourth seed Serena Williams after the American fell heavily while serving for the match against Serbia's Bojana Jovanovski. Williams was able to continue after treatment and held on to win 6-2, 6-4, but she limped off court and must be a severe doubt for her quarter-final against Daniela Hantuchova. Playing in front of her home crowd for the first time since she won at Flushing Meadows in September, an out-of-sorts Stosur was never in the hunt against the world No.54. Stosur said the shock loss wouldn't impact her campaign at the Australian Open, which starts in less than two weeks. "It was a bit of a bad day but I'll bounce back next week (in Sydney) and the week after and play a lot better, and keep getting better," she said. "Today was one match and I don't want to dwell on it. I guess it's back to the practice court -- there's no need to panic and think that it's all lost because of today." Stosur, who was born in Brisbane and grew up at the nearby Gold Coast, also lost in the second round in 2011 and had vowed before the tournament that she was ready to make up for past disappointments. But the home hero never looked comfortable against Benesova and was broken once in the first set and twice in the second in a disappointing display. "I thought she played quite well but I think I probably didn't do what I set out to do," Stosur said. "As the match went on it got harder and harder to try and stop what was happening." It was Benesova's first win over Stosur in five attempts and the first time she had even taken a set off the Australian. "I started to play against her a little differently (than previously) and it was working," Benesova said. "I was trying to keep the ball in play and not go for the big winners too early. "It's a huge step for me and I feel pretty confident right now." Sixth seed Jelena Jankovic set up a quarter-final against Francesca Schiavone with a 6-3, 6-2 win over Russia's Nina Bratchikova, while Kaia Kinepi of Estonia upset Russia's seventh seed Anastasia Pavlyuchenkova 6-0, 6-3.