History repeated itself as fourth seed Simona Halep became the biggest casualty of the Australian Open on day one, stunned by Shelby Rogers in the opening round.

Injury appeared to derail Halep, who suffered a 6-3 6-1 loss to Rogers on a sun-bathed Rod Laver Arena on Monday.

Halep was knocked out by qualifier Zhang Shuai in a sensational upset last year and the 2014 French Open finalist fell at the first hurdle again at Melbourne Park.

Coming into the season's first grand slam with just two matches under her belt in Shenzhen, Halep struggled to match it with her American opponent, ranked 52 in the world.

Cool, calm and collected, Rogers - a quarter-finalist at the French Open last year - claimed the decisive break in the sixth game of the first set to pull clear of Halep.

After dropping the opening set, Halep called for the trainer and required some attention on a leg problem and she never looked completely comfortable on court.

Rogers was relentless in the second set, converting all three of her break-point opportunities to advance to the second round.