Barty had previously not taken a set off Halep but took two in a stunning upset of the Belgian
12 January, 2019, 15:24
"I finally learned my lesson", said Barty, who had suffered two straight-sets defeats by Halep previous year.
Barty, ranked 15 in the world, surged into the quarter-finals in Sydney with a 6-4, 6-4 triumph over the reigning French Open champion and 2018 Australian Open runner-up.
Halep had the first break of serve in the second set and even served to make it 5-3 but Barty rattled off successive breaks to take the set 6-4 and complete a straight-set win over the French Open victor.
"But I really gave myself a chance".
World number one Simona Halep's first match in more than three months ended in defeat by Australia's Ashleigh Barty at the Sydney International.
She had already accounted for another French Open victor, Jelena Ostapenko, in the opening round and had an extra gear against Halep, breaking serve twice to win the first set. However, the Aussie's relentless play made for compelling viewing and resulted in another break of serve for her as she went on to pocket the first set.
"The biggest thing, I believed that I could I win".
"I had nothing to lose out here so I just came out and played with freedom. We're both on the same court and I'm just really happy I came out and executed". But I was also very close to winning.
Halep said it was challenging to play without her long-term Australian coach Darren Cahill, who is taking 12 months off the sport to focus on his family, but did not experience any back pain after taking a longer than usual recovery over Christmas.
"She played really well and deserved to win".
Barty broke Halep in the first set before the Romanian evened it up.
She will face either Belgian 10th seed Elise Mertens or Estonia's Anett Kontaveit in the next round.
Belinda Bencic, conqueror of second seed Mihaela Buzarnescu in round one, dumped out Zoe Hives 6-2 6-4.
Having defeated Spaniard Carla Suarez Navarro 6-3, 6-4 in her opening round match, the world number 16 withdrew before her match against the Dutchwoman Bertens.
Meanwhile, Alex de Minaur has cut down the equal-tallest man in professional tennis to move into the Sydney International quarter-finals for a second straight year.