Former world number one Jelena Jankovic was reduced to despair at her poor shot selection after slumping to a shock 7-6, 6-3 loss to China's Peng Shuai in the second round of the Australian on Thursday.
The seventh seeded Serbian, who arrived in Melbourne on a six-match losing streak going back to last season, was the first top 10 seed from either draw to be knocked out of the year's first Grand Slam.
"I have a bad selection of shots at the wrong times," said the 25-year-old Jankovic, a semi-finalist here in 2008.
"I couldn't afford to make the errors that I made, especially at crucial times of the match.
"I mean, as a top player -- I've been number one in the world -- it's tough to sometimes accept those mistakes. Really at times I couldn't believe I can do that, why am I doing that?"
Peng broke for a 4-2 lead in the second and served out for victory three games later, dancing around the Hisense Arena court with a huge smile on her face.
She next faces Japan's Ayumi Morita in the third round of a tournament now officially titled the "Grand Slam of the Asia/Pacific".
Peng's victory sustains China's good showing in the women's draw at the Australian Open after her compatriots Li Na and Zheng Jie both reached the semi-finals last year.
Ninth seed Li also reached the third round on Wednesday with a comfortable 6-3, 6-2 victory over Evgeniya Rodina of Russia but Zheng missed the tournament because of a wrist injury.
Clijsters races into third round in Melbourne
Kim Clijsters pulverised Spain's Carla Suarez Navarro 6-1, 6-3 to reach the third round of the Australian Open on Thursday and underline her title credentials.
The Belgian former world number one, green dress and matching visor shimmering in the Melbourne sunshine, completed the rout in 62 minutes with a crunching forehand too hot for her 62nd-ranked opponent to handle.
Third seed Clijsters, three-times grand slam champion and Australian Open runner-up in 2004, had needed just 44 minutes to whitewash Russia's Dinara Safina 6-0, 6-0 in the first round.
Beaten finalist in Sydney in the build-up to the year's first major, Clijsters tormented Suarez Navarro, who muttered angrily to herself and in the direction of her coach between points as she battled forlornly to turn the tide.