Former women's world No. 1 Jelena Jankovic failed to reach the third round at the first Grand Slam of the season here on Thursday by losing to China's unseeded Peng Shuai in straight sets.
The 25-year-old Serbian, seventh seed of the women's singles, became the highest-ranked woman to be out of the top 32.
Leading 6-1 in seven previous matches against her opponent, Jankovic was toppled 7-6 (3), 6-3 in one hour and 50 minutes, equalling her earliest finishes in the nine appearances at the Melbourne Park and recording the earliest one since 2007.
"I had a bad day," said Jankovic. "I was leading I think 4-1 and had everything under my control. I was playing pretty well. But then I just had some loose errors and she played as well some good points.
"And little by little, she was getting her momentum, and I started completely going down. "
Jankovic made 36 unforced errors against Peng's 20 and suffered a total of 13 break points in which she saved nine.
"I have a bad selection of shots at the wrong times. I couldn't afford to make the errors that I made, especially at crucial times of the match. I mean, as a top player, it's tough to sometimes accept those mistakes. Really at times I couldn't believe I can do that, why am I doing that," she said.
However, she added that it was good for her to stay healthy and could really compete out there.
"I just have to now continue to work hard and work on my game and really build on my confidence," she said. "Hopefully I will get more matches in the future and just keep getting better."