Ash Barty stuns world No.1 Simona Halep

Darren Walton
Ashleigh Barty shocked world No.1 Simona Halep at the Sydney International

Ashleigh Barty's summer expectations continue to grow, the Queenslander upstaging world No.1 Simona Halep five days out from the Australian Open.

Focused from the get go, Barty surged into the Sydney International quarter-finals with a 6-4 6-4 triumph over the reigning French Open champion and 2018 Australian Open runner-up.

The Australian No.1 served five aces, no double-faults and broke Halep three times to reverse two previous losses to the Romanian last August.

"I finally learnt my lesson," a beaming Barty said.

"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. We're both out here on the same court. Just very happy I was able to come out and executive.

"I felt like it was really clean, considering the conditions.

"It was very swirly down at court level so I figure if I'm going to play 'Sim' at any time, it's her first match and in conditions like this.

"So I was very happy I was able to make the most of it. Yeah, extremely pleased."

Next up on Thursday for the world No.15 is either Belgian 10th seed Elise Mertens, 2016 Olympic champion Monica Puig or Estonian Anett Kontaveit.

While Barty marches on in pursuit of a second straight final in Sydney, Halep's defeat leaves her Australian Open preparations in tatters.

The 27-year-old hasn't won a match in five months after an injury-marred end to 2018 and will also be in Melbourne without a coach after parting ways with Australian mentor Darren Cahill, who can longer commit to Halep due to family reasons.