MELBOURNE (AFP/REUTERS) - Wimbledon women's singles champion Garbine Muguruza became the biggest casualty of the Australian Open so far - stunned by Chinese Taipei's Hsieh Su-wei in straight sets on Thursday (Jan 18).
The third seed, whose preparation had been hampered by a thigh injury, trailed the world No. 88 from the beginning, before losing 6-7 (1-7), 4-6 in 1hr 59min on Rod Laver Arena.
Hsieh, whose previous best at Melbourne Park was a last-16 defeat by Justine Henin 10 years ago, goes on to meet 26th seed Agnieszka Radwanska of Poland in the third round.
But top seed Simona Halep eased fears over her fitness with a brisk 6-2 6-2 victory over Canada's Eugenie Bouchard to reach the third round.
The Romanian world No. 1 sprained her ankle in her first round match at Melbourne Park on Tuesday but showed no sign of restricted movement in a 65-minute romp on Margaret Court Arena.
Marching around the court like she meant nothing but business, she broke Bouchard seven of the eight times the Canadian served to set up a third-round meeting with American Lauren Davies.
However, ninth seed Johanna Konta's campaign also came to a sticky end with world No. 123 Bernarda Pera sending the Briton tumbling out of the second round with a 6-4, 7-5 upset in blazing sunshine on Court 2.
A lacklustre serving display from the British No. 1 allowed left-hander Pera ample opportunity to showcase her powerful returns off both sides and the 23-year-old American duly delivered.
A single break of serve for 5-4 was enough to sew up the first set after 39 minutes when Konta sent a backhand long and lucky loser Pera was soon over the Briton's serve in the second.
Konta, a semi-finalist at Melbourne Park in 2016 and quarter-finalist last year, saved four match points but Pera was not to be denied and set up a meeting with Barbora Strycova when the Briton fluffed an overhead volley.
Meanwhile, former world No. 1 Angelique Kerber celebrated her 30th birthday on Thursday with an emphatic 6-4 6-1 win over Donna Vekic to set up an intriguing third-round clash of former champions with Maria Sharapova.
The resurgent German, who broke a 27-tournament title drought with victory at the Sydney International in the lead-up, is now riding a seven-match winning streak as she looks to recapture the form that propelled her to the 2016 title at Melbourne Park.
In scorching conditions on Margaret Court Arena, she gave 52nd-ranked Vekic the run-around with a series of deft drop-shots and closed out the one-sided match with a confident cross-court smash.
Sharapova, also a former No. 1, suffered a late wobble in the blazing Centre Court heat before easing past 14th seed Anastasija Sevastova 6-1, 7-6 (7-4).
With the temperatures soaring, the former champion fired a barrage of winners past the Latvian to roar through the first set in 23 minutes at Rod Laver Arena.
The 30-year-old wavered when serving for the match at 5-4, allowing Sevastova to drag the match into a tie-break, but the Russian doubled down on her baseline firepower to raise three match points quickly.
She closed out the match on the second when Sevastova clubbed a forehand long.