MELBOURNE, Australia (AFP) — Defending champion Novak Djokovic oozed class in an awesome performance at the Australian Open yesterday as Maria Sharapova stormed into the third round without dropping a game.

Djokovic, up last on centre court and chasing the first Australian Open hat-trick since the 1960s, wasted little time in dispatching America's Harrison, who was never close to taking his first ever set off the Serb.

The world number one, handed an uncomplicated draw after the withdrawal of Rafael Nadal, was irresistible as he blew away Harrison, 6-1, 6-2, 6-3, but afterwards he spared a thought for his floundering opponent.

"It's a pity for him, I don't think he played his best. It's probably just the occasion, playing on centre court," Djokovic said.

With Roger Federer and Andy Murray both playing today, David Ferrer and Tomas Berdych also pressed their outside claims as they reached the third round, along with 2006 finalist Marcos Baghdatis and Japan's Kei Nishikori.

And as women's pre-tournament favourite Serena Williams, a day after rolling her ankle, skipped a public practice session, Sharapova showed why she must be taken seriously for her second Australian Open title.

Sharapova, the world number two, had been flawless in her 6-0, 6-0 opener against Olga Puchkova, and she remarkably repeated the scoreline -- a feat not achieved at a Grand Slam since 1985 -- against Japan's Misaki Doi.

Standing in Sharapova's way in round three is Serena's sister Venus, who is climbing back up the rankings after a long spell of illness and dispatched France's Alize Cornet on the centre court.

Fourth seed Agnieszka Radwanska smoothly put away Irina-Camelia Begu to reach the third round, where she was joined by German fifth seed Angelique Kerber and China's sixth seed Li Na.

"Australia for me -- I really believe I can win this Grand Slam," said 2011 runner-up Li, after her 6-2, 7-5 victory over Olga Govortsova.

But there was misery for Australian favourite Samantha Stosur, the ninth seed and 2011 US Open champion, who threw away five consecutive third-set games as she crashed out against China's Zheng Jie.

Stosur, who suffered first-round flops at WTA events in Brisbane and Sydney this year, was leading 5-2 in the third set but she choked in front of her home fans and ultimately double-faulted to hand Zheng victory, 6-4, 1-6, 7-5.

In the men's draw, Spanish fourth seed Ferrer was extended by 125th-ranked American Tim Smyczek before winning, 6-0, 7-5, 4-6, 6-3, while Berdych, the fifth seed, enjoyed a straight-sets win over Frenchman Guillaume Rufin.

Elsewhere on day three, Japan's Nishikori powered on with a straight-sets victory over Argentina's Carlos Berlocq, and Spanish 10th seed Nicolas Almagro went through in three sets.

Towering Pole Jerzy Janowicz succumbed to the tournament's first meltdown, after he fell to his hands and knees and repeatedly screamed, "How many times?" over a line call during his win over India's Somdev Devvarman.

Footage of the incident, which follows Baghdatis's tantrum when he smashed four racquets in swift succession last year, quickly circulated on the Internet.

But there was agony for the luckless Brian Baker, who has battled back from six years on the sidelines following a series of operations, when he collapsed with a serious knee injury while playing fellow American Sam Querrey.