American powerhouse Serena Williams ensured Hungarian journeywoman Greta Arn's first visit to Rod Laver Arena was a short one as she continued to build her own case for a sixth Australian Open singles crown.

Williams entered the event under a major cloud after a recent ankle injury.

But that is beginning to seem a faint memory after she stormed into the fourth round with Saturday night's 6-1 6-1 win.

It was the first time in the Open third round for 32-year-old world No.92 Arn, whose earnings for her entire 16-year career are less than half of what Williams made last year, despite the American missing half the year through injury.


But there was never a hint of a fairytale result as Williams took less than an hour to book a fourth round berth for the ninth time.

There was a moment of relief for the Hungarian when she finally found her way onto the scoreboard in the sixth game, having to save a set point to do so.

But that was barely a speed bump in Williams' race through the match.

It was the former world No.1's third comfortable straight sets win of the tournament, but she still described her form as "rusty".

"I am nowhere near where I want to be," Williams said.

"I was a little rusty. I'm just trying to play through the rust."

But Williams, who has claimed the title on five of her past seven trips to Melbourne Park, already looks to be finding the kind of form to have her looming large as a contender this year, particularly given her seemingly unrestricted physical condition.

Williams will next meet unseeded Russian Ekaterina Makarova, before a potential quarter-final clash with 2008 Open winner Maria Sharapova.

Sharapova has also been in excellent touch, dropping a total of five games in the first three rounds.