Serena Williams admits she is still nowhere near her best form despite making it through to the Australian Open last-16 with a 6-1 6-2 win over Greta Arn (Williams 3/1 fav Australian open outright).

The five-time champion sealed the victory over her Hungarian opponent in less than an hour and will now play Ekaterina Makarova in the fourth round.

It was a straight forward win that belied Williams’ fitness problems that have hampered her game over the past 12 months.

The American has won the tournament in Melbourne on her last two appearances – in 2009 and 2010 – but an injury-hit 2011 meant she was forced to miss out on last year’s competition.

The 30-year-old has played just one tournament since the US Open last August and admits she is still a long way off match sharpness.

“I’m nowhere near where I want to be, but I’m trying to play through it,” said Williams.

“I’m really rusty. I’m just trying to play through the rust.”

Elsewhere there were victories for seeded trio Maria Sharapova, Sabine Lisicki and 7/2 joint second favourite Petra Kvitova.

However, ninth seed Marion Bartoli crashed out to China’s Zheng Lue in straight sets.