What to expect at Australian Open Day 2

Halep faces tricky test against Kanepi in Melbourne opener

Simona Halep begins her Australian Open campaign against Kaia Kanepi, on Tuesday, in a rematch of their US Open meeting which the world number one lost in straights sets.

The Romanian has struggled for form and fitness since that first-round defeat at Flushing Meadows last year and comes into the year's first Grand Slam short of preparation after a back injury ended her 2018 season prematurely.

Defeat to local hope Ashleigh Barty in the opening round of the Sydney International last week means Halep has played only one match ahead of a potentially tricky test against world number 71 Kanepi.

The top seed has recovered fully from a herniated disk that she aggravated at the China Open in September, but said that she was feeling a bit behind the curve.

"I'm motivated. But it's a little bit different because last year I had about 10, 15 matches before Melbourne; now I have one, which I lost," said Halep, who reached the final at Melbourne Park last year.

"I took the risk staying home a little bit longer. I rested because I felt like I'm exhausted after those tournaments and also the year that I had."

Kanepi will be out to prove that her victory over the French Open champion was no fluke but the 33-year-old could be short of match practice herself, having not featured since reaching the fourth round in New York after aggravating an existing injury.

Serena Williams, who resumes her quest for a record-equalling 24th Grand Slam title, plays unseeded German Tatjana Maria at Rod Laver Arena in the second match on Tuesday.

Top seed Novak Djokovic, who made a spectacular return to form last year and won the last two Grand Slams, takes on American Mitchell Krueger in the evening session.