Melbourne - Wimbledon champion Garbine Muguruza refused to blame her heat-blistered feet as she became the biggest casualty of the Australian Open so far on Thursday.
The third seed, whose preparation was hampered by a thigh injury, was always trailing against the 88-ranked Hsieh Su-wei from Taiwan before being edged out 7-6 (7/1), 6-4 in one hour and 59 minutes on Rod Laver Arena.
"I maybe could have done things better, but at the end, she deserves to win. That's really it," Muguruza told reporters.
Two-time Grand Slam champion Muguruza struggled from the start to keep pace with the tenacious 32-year-old whose last WTA Tour singles title came at Guangzhou back in 2012.
The tall Spaniard had a medical timeout at 2-5 in the first set and after having a blistered foot re-taped looked briefly regalvanised.
Muguruza said her feet were suffering in the heat as temperatures soared above 39 degrees Celsius.
"I think the surface of the court, I don't know how much heat, it's terrible, very, very hot, and it's easy to get blisters and red," she said.
"I don't think that was the reason why today it didn't go my way. It was already wrapped (foot), but very quickly I started to feel a blister was coming, and I'd rather prevent it than having the problem after."
Muguruza then broke back twice but Hsieh, who works closely with former Australian Open tournament director Paul McNamee, ran away with the tiebreak 7-1.
"He's always been around me and supported me and was amazing," she said of McNamee's influence.
"My goal to hire him at the beginning was to win a Grand Slam," she added.
Muguruza saved a first match point in the second set to get back to 5-4 but Hsieh made no mistake in the next game.
"I knew she was going to give me a lot of pressure," said Hsieh, who was ranked number one in doubles for five weeks in 2014.
"At 5-4 I thought I'd keep hanging there and try and take my spot," she said.
"It's never easy to play against top 20 girls. I think mentally for sure they are much better, so when we go on the court we have to forget who we are playing and focus on our game."
Hsieh, whose previous best at Melbourne Park was a last-16 defeat to Justine Henin 10 years ago, goes on to meet 26th seed Agnieszka Radwanska of Poland in the third round.
Results from the Australian Open on Thursday:
Albert Ramos (ESP x21) bt Tim Smyczek (USA) 6-4, 6-2, 7-6 (7/2)
Marton Fucsovics (HUN) bt Sam Querrey (USA x13) 6-4, 7-6 (8/6), 4-6, 6-2
Nicolas Kicker (ARG) bt Lukas Lacko (SVK) 6-2, 7-5, 1-6, 7-5
Dominic Thiem (AUT x5) bt Denis Kudla (USA) 6-7 (6/8), 3-6, 6-3, 6-2, 6-3
Tomas Berdych (CZE x19) bt Guillermo Garcia-Lopez (ESP) 6-3, 2-6, 6-2, 6-3
Fabio Fognini (ITA x25) bt Evgeny Donskoy (RUS) 2-6, 6-3, 6-4, 6-1
Adrian Mannarino (FRA x26) bt Jiri Vesely (CZE) 6-3, 7-6 (7/4), 5-7, 6-3
Novak Djokovic (SRB x14) bt Gael Monfils (FRA) 4-6, 6-3, 6-1, 6-3
Chung Hye-On (KOR) bt Daniil Medvedev (RUS) 7-6 (7/4), 6-1, 6-1
Julien Benneteau (FRA) bt David Goffin (BEL x7) 1-6, 7-6 (7/5), 6-1, 7-6 (7/4)
Juan Martin Del Potro (ARG x12) bt Karen Khachanov (RUS) 6-4, 7-6 (7/4), 6-7 (0/7), 6-4
Bernarda Pera (USA) bt Johanna Konta (GBR x9) 6-4, 7-5
Barbora Zahlavova Strycova (CZE x20) bt Lara Arruabarrena (ESP) 6-3, 6-4
Maria Sharapova (RUS) bt Anastasija Sevastova (LAT x14) 6-1, 7-6 (7/4)
Agnieszka Radwanska (POL x26) bt Lesya Tsurenko (UKR) 2-6, 7-5, 6-3
Caroline Garcia (FRA x8) bt Marketa Vondrousova (CZE) 6-7 (3/7), 6-2, 8-6
Lauren Davis (USA) bt Andrea Petkovic (GER) 4-6, 6-0, 6-0
Lucie Safarova (CZE x29) bt Sorana Cirstea (ROM) 6-2, 6-4
Karolina Pliskova (CZE x6) bt Beatriz Haddad Maia (BRA) 6-1, 6-1
Hsieh Su-wei (TPE) bt Garbine Muguruza (ESP x3) 7-6 (7/1), 6-4
Aliaksandra Sasnovich (BLR) bt Mirjana Lucic-Baroni (CRO x28) 6-3, 6-1
Angelique Kerber (GER x21) bt Donna Vekic (CRO) 6-4, 6-1
Ana Bogdan (ROM) bt Yulia Putintseva (KAZ) 1-6, 6-2, 6-3
Naomi Osaka (JPN) bt Elena Vesnina (RUS x16) 7-6 (7/4), 6-2
Madison Keys (USA x17) bt Ekaterina Alexandrova (RUS) 6-0, 6-1