Fourth seed Halep shocked at Aussie Open

Romania's Simona Halep hits a return against Shelby Rogers of the US during their women's singles match on day one of the Australian Open tennis tournament in Melbourne on Jan 16, 2017. (Photo: PETER PARKS/AFP)

The out-of-sorts Romanian, who called for medical attention after losing the first set, went down 6-3, 6-1 on day one in hot conditions on Rod Laver Arena.

It was a case of deja vu for the right-hander, who was sent packing at the same stage last year by Chinese qualifier Zhang Shuai.

Halep is one of the fastest movers on court but she was missing her usual zip against the 24-year-old American, who reached the French Open quarter-finals last year.

Rogers, in only her second Australian Open appearance, was ecstatic at claiming such a big scalp.

"It's pretty incredible, I played really well today," said Rogers, ranked 52 in the world.

"There are no easy matches at this level so I am happy to get through and I take a lot of confidence from today."

Playing the first match of the tournament on centre court, Rogers held serve first up when Halep sent a backhand wide as both players adjusted to the conditions.

As sweat quickly started dripping off them, it went with serve to 2-2 in a close fought contest as Halep was forced to save two break points to stay at level pegging.

Rogers, coming off a run to the quarter-finals at the Hobart International, finally got the break in the sixth game to lead 4-2 when Halep smashed a volley into the net.

The sluggish Romanian saved two set points on her next service game but Rogers wasn't to be denied and she wrapped up the set 6-3 in a gruelling 46 minutes.

The usually tenacious Halep was clearly struggling and she called for the trainer at the changeover, and was seen to take a tablet.

It didn't appear to help with a confident Rogers breaking in the third game of the second set to go 2-1 ahead before quickly reeling off the last four games.

Rogers' reward is a second-round clash against either Australian qualifier Ashleigh Barty or Germany's Annika Beck.