Sharapova, a victor at Melbourne in 2008, signalled her intent with a rare 6-0, 6-0 double bagel demolition of Britain's Harriet Dart.
The 22-year-old Dart had a game point on her serve in the eighth game of the match, but Sharapova rallied to break the British player and continue the rout.
Her opponent, a former top-50 player, was too erratic to trouble the three-times Grand Slam victor, committing nearly three times as many unforced errors as Kerber.
Nadal won the Australian Open in 2009 and is bidding to become the first man in the Open era to win each Grand Slam on two or more occasions. You know, you're doing all the right things, she's making a few errors, you're comfortable, easy to get complacent and, you know, complacency is not great.
Up next for Sharapova is Rebecca Peterson, who beat Sorana Cirstea 6-4, 6-1.
Rafael Nadal celebrates winning the match against Australia's James Duckworth. In the second set, the break came in the third game for Wozniacki and it proved to be enough.
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The Briton prevailed 6-0 4-6 7-6 (10-6) as she sent the former semi-finalist packing, Boulter recording the biggest win of her career to date. "I know it very well".
In an interview during an event held by Kia Motors earlier this week at the Australian Open, the 17-time Major victor Rafael Nadal commented on his partnership with the auto brand with which he is connected by a contract until 2020.
Reilly Opelka, a 21-year-old who eliminated No. 9 John Isner in an all-U.S. showdown in the first round, held a 67-2 ace advantage - and a 15-inch (38-centimetre) height advantage - against Thomas Fabbiano but lost to the Italian 6-7 (15), 6-2, 6-4, 3-6, 7-6 (5).
The Australian Open has not seen a home female victor since 1978 but many believe Barty could be the one to break that run, her impressive showing in Sydney prior to the first slam adding fuel to the fire.
Nadal will face another Australian, Matt Ebden, in the second round on Wednesday.
Tomas Berdych sent 2018 Australian Open semifinalist Kyle Edmund home early with right away with a 6-3, 6-0, 7-5 win over the No. 13 seed on Melbourne Arena.