The 32-year-old Hsieh is a former top-ranked doubles player who had only one previous win over a top-10 player and whose career-high singles ranking peaked at 23 in 2013. "I think today she played well".
"I maybe could have done things better but at the end, she deserves to win", she said. Radwanska, who called for the trainer after the first set and sported strapping on her left knee, fought bravely in the second set but the twice Melbourne semi-finalist could not find a way to stop Hsieh.
The tall Spaniard had a medical timeout at 2-5 in the first set and after having a blistered foot re-taped looked briefly regalvanized.
Third-seed Muguruza was unable to deal with the unusual game of Hsieh in hot and windy conditions at Melbourne Park and slumped to a 7-6 (7-1) 6-2 defeat.
Wimbledon champion Garbine Muguruza struggled with the heat and against Hsieh Su-wei's game, losing 7-6 (1), 6-4 on Day 4 as the upsets intensified at the Australian Open.
Tomas Berdych has ended the Australian Open campaign of Juan Martin del Potro, beating the Argentinian 6-3, 6-3, 6-2 in a third-round match. "I did my job in two sets against someone that's been troubling in the past for me", said Sharapova, who missed last year's tournament while serving a 15-month doping ban.
WOMEN, 2ND RD Bernarda Pera (USA) bt Johanna Konta (Gbr) 6-4 7-5, Karolina Pliskova (Cze) bt Beatriz Haddad Maia (Bra) 6-1 6-1, Naomi Osaka (Jpn) bt Elena Vesnina (Rus) 7-6 (7-4) 6-2, Madison Keys (USA) bt Ekaterina Alexandrova (Rus) 6-0 6-1.
Making it through the furnace-like conditions though were world No. 1 Simona Halep, sixth seed Karolina Pliskova, eighth seed Caroline Garcia and five-time Grand Slam victor Maria Sharapova, who set up an enticing third-round clash with Angelique Kerber tomorrow. But I felt today much better, so that's the good news.
Hsieh was especially productive on her backhand, guiding 12 winners past her opponent, the last one coming on match point. "I hit the ball really well and it is alway tough against her as she hits hard from the baseline".
In what was the longest game of the match, Hsieh prevailed with an array of fantastic winners as both players were putting up a good show for the Margaret Court Arena crowd. "I'm happy I didn't buy one". "I want to be playing against opponents that are former Grand Slam champions".
No. 5 Dominic Thiem rallied from two sets down to defeat 190th-ranked American qualifier Denis Kudla 6-7 (6), 3-6, 6-3, 6-2, 6-3 in the second round. "I want to go further than fourth round and I'll give everything to do it for the first time", he said.