An out-of-sorts Simona Halep suffered a shock first-round exit at the Australian Open, falling to a 6-4 6-3 defeat at the hands of Zhang Shuai.

After Caroline Wozniacki was sent packing on Monday and Venus Williams lost on Tuesday, second seed Halep - who is still without a grand slam title - became the biggest casualty of the women's draw so far.

The Romanian, who made the quarter-finals in the past two years, has been hampered by an Achilles injury in the build-up to the tournament and that perhaps played a part in her defeat to Zhang - the Chinese winning a match at a grand slam for the first time.

Halep made a sluggish start as Zhang raced into a 4-0 lead, but the momentum swung in the Romanian's favour when a huge double backhand earned her a first break and, after wasting three break points at 4-2, she clawed the second back when Zhang found the net.

Halep's troubles on serve continued, though, and she handed the initiative straight back to gift Zhang the opening set.

A Zhang double fault gave Halep an early break in the second set, but she once again shocked her opponent with a stunning forehand to level at 3-3. 

Halep's misery continued as she was broken to love in game eight - the fifth time she surrendered serve - and Zhang grasped her opportunity to book a spot in round two.

A visibly distressed Halep was left weeping in her chair as she came to terms with her unexpected exit.