World number one Simona Halep crashed to a straight-sets defeat against unseeded Ashleigh Barty in the second round of the Sydney International on Wednesday.
Halep, playing in her first tournament since a back injury cut short her 2018 season in September, lost 6-4 6-4 in 87 minutes with the result dealing a blow to her Australian Open preparations.
Australian Barty, who is ranked 15th in the wor zld, fired 26 winners and won four out of seven break points as she recorded her first victory over a reigning world number one.
“I finally learned my lesson,” said Barty, who had suffered two straight-sets defeats by Halep last year.
“She gave me a belting in Montreal. I learnt a little bit more in Cincinnati, but today I knuckled down and really thought about it and really gave myself a chance.
“The biggest thing, I believed that I could I win. Just very happy I was able to come out and execute.”
The 22-year-old Barty was rewarded with a quarter-final clash against Belgian Elise Mertens, who raced past Estonia’s Anett Kontaveit 6-3 6-1.
Kazakh qualifier Yulia Putintseva came back from a set and a break down to beat fourth seed Sloane Stephens 3-6 7-6(4) 6-0 in a roller-coaster second round encounter.
It was Putintseva’s sixth career top 10 victory, and second consecutive win over Stephens following an equally dramatic three-set triumph in Nuremberg last year.
Men’s top seed Stefanos Tsitsipas eased past Argentine Guido Andreozzi 6-3 6-4 to earn his first Tour-level win over of the new season.
Greek youngster Tsitsipas, who won the ATP Next Gen Finals in Milan last year, broke his opponent three times and held off a late comeback to move into the quarter-finals.
The world number 15 will next face Italian Andreas Seppi, who beat Slovakia’s Martin Klizan 7-6(2) 6-2.
Home favourite Alex de Minaur was at his ruthless best to dismiss American qualifier Reilly Opelka 6-4 7-6(5), while third seed Diego Schwartzman broke Spaniard Guillermo Garcia-Lopez’s serve five times en route to a 6-2 6-3 win.