The Romanian, who cut short her 2018 season with a back injury, was beaten 6-4 6-4 by the world number 15 in the second round after a first-round bye.

French Open champion Halep, 27, who was runner-up at last year's Australian Open, has started 2019 without a coach.

The first Grand Slam of the year starts in Melbourne on Monday.

Barty fired 26 winners on her way to her first victory over a world number one. She will face either Belgian 10th seed Elise Mertens or Estonia's Anett Kontaveit in the next round.