Second seed Federer, third seed Nadal and sixth seed Andy Murray all enjoyed straight sets wins, with rising stars Simona Halep, Eugenie Bouchard and Grigor Dimitrov also progressing on a cool Melbourne day.

World number two Sharapova, looking for her first Australian title since 2008, swept aside Croat Petra Martic 6-4, 6-1.

"I made a few too many unforced errors but overall I'm glad I got through," said the Russian, adding that she was reaping the benefits of a strong lead up to the tournament when she won the Brisbane International.

It was a different story for fifth seed Ivanovic, a former world number one who came to Melbourne full of
confidence after a stellar 2014 that saw her climb the rankings.

She started well against unheralded world number 142 Lucie Hradecka of the Czech Republic, easily winning the first set, but then went to pieces, eventually crashing 1-6, 6-3, 6-2.

"I really struggled to find my rhythm today, I was just a little bit lost," said the stunned Serb, a perennial crowd favourite in Australia where she has family.

Ninth seeded German Angelique Kerber also failed to live up to the hype, eliminated in three sets by Romanian Irina-Camelia Begu.

Swiss great Federer, gunning for his fifth Australian crown and 18th Grand Slam title, had no such problems and was in full control against Taiwan's Lu Yen-Hsun.

He went through the motions for a 6-4, 6-2, 7-5 win and welcomed the workout.

"It's early in the season and it's tough to get rhythm, especially in the first round, but this court plays nice and we had some great rallies so it was a nice match," said Federer.

His long-time rival Nadal showed few signs of the injuries that disrupted his 2014 season in dispatching Russian Mikhail Youzhny 6-3, 6-2, 6-2, conceding just one break point on his serve.

"A very positive result for me," said Nadal, who missed the end of last year due to appendicitis and has also struggled with ongoing back and wrist injuries.

"It was a comfortable victory that give me some confidence," added the Spanish 14-time Grand Slam champion.

- Testing workout -

Top seeds Serena Williams and Novak Djokovic and defending men's champion Stan Wawrinka are in action on Tuesday.

Women's champion Li Na of China has retired and is not taking part, although she is a guest of honour and announced to the Rod Laver crowd that she was expecting her first child.

Murray was given a testing workout by promising Indian Yuki Bhambri before emerging a 6-3, 6-4, 7-6 (7/3) winner.

The Scot, who is bidding to become the first player to win the Australian Open after losing three finals at Melbourne Park, said he was pleased with the state of his tennis under coach Amelie Mauresmo.

"I've been playing very well in the practices and striking the ball cleanly in the matches. If I keep that up
I'll keep getting better each round," he said.

World number three Halep opened the 2015 proceedings with the wind swirling around Rod Laver Arena, carving out a 6-3, 6-2 defeat of Italy's Karin Knapp.

The Romanian, a quarter-finalist at Melbourne Park last year, is looking to build on a breakthrough 2014 when she reached the French Open final and the semi-finals at Wimbledon.

Seventh seed Bouchard, a semi-finalist in 2014, posted a solid 6-2, 6-4 win over Germany's Anna-Lena Friedsam while 10th seed Dimitrov progressed with an easy 6-2, 6-3, 6-2 victory over German Dustin Brown.

At the vanguard of the new order of younger men's players, Dimitrov said he was happy with his start but the windy conditions were challenging.

"I think it was just a little tough for everyone to get into that rhythm, to get used to the court. It was pretty windy today," he said.

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