Top seed Rafael Nadal turned on the style as he launched his bid for a record-equalling 20th Major title at the Australian Open on Tuesday, but falling star Maria Sharapova hit a career low.

Nadal, one shy of Roger Federer's Grand Slam mark, dropped only five games as he swatted aside Bolivia's Hugo Dellien 6-2, 6-3, 6-0 in just over two hours at a sunny Rod Laver Arena.

"It was a positive start," said the reigning Roland Garros and US Open champion, wearing a bright pink singlet and matching trainers.

Rafael Nadal
Spain's Rafael Nadal beat Bolivia's Hugo Dellien in the first round Photo: AFP / John DONEGAN

"What you want in the first round is just to win, and it's better if it's in straight sets."

He joins Federer and defending champion Novak Djokovic in round two in Melbourne as the Big Three look to tighten a stranglehold that has brought them all but one of the last 14 Australian Open titles.

Nadal, the first player to be world number one in three different decades, is still thriving at 33 but it's a different story for five-time Grand Slam winner Sharapova, 32.

Sharapova, playing on a wildcard as she wrestles with a shoulder problem, lost 3-6, 4-6 to Croatian 19th seed Donna Vekic, making her an opening-round loser at three straight Grand Slams for the first time.

Maria Sharapova
Maria Sharapova has lost in the first round at the last three Grand Slam tournaments Photo: AFP / John DONEGAN

The future looks uncertain for the former world number one, who won Wimbledon when she was just 17 but has not reached a Grand Slam final since she lifted the 2014 French Open trophy.

"I can speak about my struggles and the things that I've gone through with my shoulder, but it's not really in my character to," Sharapova said.

"I was there, I put myself out there (playing). As tough as it was, I finished the match -- it wasn't the way that I wanted."

Fabio Fognini
Italy's Fabio Fognini came back from two sets down to beat Reilly Opelka Photo: AFP / DAVID GRAY

Britain's Johanna Konta, a two-time Slam semi-finalist, also fell at the first hurdle as she battles to overcome a knee problem, losing 4-6, 2-6 to unseeded Tunisian Ons Jabeur.

On a bumper day of 96 first-round matches, after rain wiped out half of Monday's schedule, former US Open champion Marin Cilic and Milos Raonic both moved safely through.

Italy's Fabio Fognini, two sets down against America's Reilly Opelka when their match was suspended on Monday, returned to win it in five on Tuesday after a stormy encounter when both players argued furiously with the umpire.

"You're pathetic. You give me one warning after one throw (of my racquet). He's thrown his three or four times, bro," Opelka, who stands 6ft 11ins (211cm) to Fognini's 5ft 10ins, told the chair official.

A new star emerged in 18-year-old Italian Jannik Sinner, last year's NextGen champion, who earned his first Grand Slam victory 7-6 (7/2), 6-2, 6-4 against Australia's Max Purcell.

Later, Australia's Nick Kyrgios, who has spearheaded fundraising efforts for the country's deadly bushfire disaster, opens his campaign against Lorenzo Sonego of Italy.

Russia's Daniil Medvedev, who took Nadal to five sets in last year's US Open final, will play 2019 Melbourne quarter-finalist Frances Tiafoe of America.

And former world number one Angelique Kerber, the 2016 champion, will round off the evening on Rod Laver Arena against unseeded Italian Elisabetta Cocciaretto.

Pollution from the bushfires, which dominated the build-up to the first Grand Slam of the year, was blown away by Monday's heavy rain.

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Australian Open Rafael Nadal Roger Federer Novak Djokovic