Bulgarian qualifier Tsvetana Pironkova has set up a semi-final showdown with title favourite Petra Kvitova at the Sydney International after a surprise win over third seed Sara Errani.
Second-seeded Kvitova was the first woman through to the semis after removing fellow Czech Lucie Safarova in straight sets on Wednesday to post her 300th career win.
The highest-ranked player left in the draw after Tuesday’s demise of top-seeded titleholder Agnieszka Radwanska, Kvitova advanced to the last four with a 7-6 (7-4) 6-2 defeat of Safarova.
And the seeds continued to tumble with the 107-ranked Pironkova accounting for Italian world No.7 Errani in straight sets 7-6 (7-2) 6-3.
Pironkova, a one-time Wimbledon semi-finalist, needed just under two hours to dispose of Errani, who was sporting heavy strapping on her right thigh and took an injury time out in the second set to get treatment on her lower back.
The other two quarter-finals, featuring Americans Bethanie Mattek-Sands and Madison Keys and German fifth seed Angelique Kerber against Spaniard Carla Suarez Navarro, will be played on Wednesday night.