Fifth seed Ana Ivanovic was knocked out of the Australian Open first round on Monday when she was upset by doubles specialist Lucie Hradecka 1-6, 6-3, 6-2.
The former French Open champion had roared through the first set in 21 minutes before the wheels fell off at Rod Laver Arena.
Hradecka, who played only three WTA level events in 2014, raced through the next two sets in just over an hour to send the Serb packing and set up a second-round encounter with Slovenia's Polona Hercog or China's Wang Qiang.
Ivanovic is the highest seed to exit so far, with number 32 Belinda Becic and 27th seed Svetlana Kuznetsova also first-round casualties.
Hradecka, who played only three WTA events last year, caused the biggest upset by overhauling former French Open champion Ivanovic and squealed in disbelief after the out-of-sorts Serb bowed out with her 30th unforced error.
"I was so nervous in the beginning and same in the end. My hand was shaky," a beaming Hradecka told the Rod Laver Arena crowd.
Kuznetsova sent packing
Former Wimbledon finalist Sabine Lisicki was another high-profile casualty, the 28th-seeded German upset in three sets by 71st-ranked Frenchwoman Kristina Mladenovic.
Two-time Grand Slam champion Svetlana Kuznetsova, seeded 27th, was also sent packing by Frenchwoman Caroline Garcia and her 23rd seeded Russian compatriot Anastasia Pavlyuchenkova soon followed, going down to Belgium's Yanina Wickmayer.