Key threats to Ash Barty's maiden Australian Open title win have begun to find their groove at the Sydney Tennis Classic.
Barty will be the top seed for the first Major of the year, starting January 17, when the Australian ace began her summer in impressive fashion by winning the Adelaide International last week.
After Barty's refusal to play in Sydney, world No. 1 rivals have found their form, progressing to the quarter-finals of the tournament.
Ons Jabur defeated two-time Wimbledon champion Petra Kvitova 6-4, 6-4 to reach the last eight.
"I am working a lot on myself and my mindset," said Jaboor, seeded ninth at Melbourne Park.
"Everyone knows that if I decide to do something I do it and I'm going to go with that mindset from now on."
The Tunisian will now face world number 7 Annette Kontaveit, with the Estonian showing her class to beat Romania's Elena-Gabriela Russe 6-3, 6-1.
Spanish world number 3 Garbine Muguruza won the second set 6-1 7-6 (7-4) against Ekaterina Alexandrova and advanced to the quarterfinals against 26th-ranked Daria Kasatkina.
The Russian defeated defending Australian Open champion Sofia Kenin earlier this week with a 6-3, 6-4 win over Belgium's Elise Mertens.
Kazakhstan's Elena Rybkina was unable to support her win over US Open champion Emma Radukanu as world number 13 was forced to pull out of her bout with Caroline Garcia due to a thigh strain.
Garcia will face Czech world number four Barbora Krejcikova, who beat Romania's Jacqueline Edina Christian 6-1, 7-5.
A tie between Olympic gold medalist Belinda Bencic and France's Oisen Dodin was delayed due to rain when Dodin was set up.
Australia's Ajla Tomljanovic met world number 9 Paula Badosa of Spain to complete the day's action.