Melbourne - Third seed Dinara Safina stayed on course for a shot next week at the number one WTA ranking, gaining a Friday win for the Safin family hours before her brother Marat was to face Roger Federer.

Safina, the losing finalist at the French Open, reached the fourth round in Melbourne for the first time in her career, posting a 6-2 6-2 win over Kaia Kanepi.

Safina is one of three women chasing Jelena Jankovic in the rankings with a title next Sunday enough to assure the 22-year-old of the breakthrough top spot.

Russia's number 10 seed, Nadia Petrova, advanced without a fight as opponent Galina Voskoboeva quit with a back injury after losing the first set 6-1.

Safina's big brother Marat, the 2005 Melbourne champion, was hoping to repeat his semi-final success that year over Federer as he faced the on-form Swiss in a night showcase, third-round match.

But Safina, while planning to watch that encounter in person, had her own reasons to celebrate.

"There's a first time for everything," she said of her trip to the final 16. "Twice I lost in the third round. This is the third time. It should be the luckiest one."

Safina faces off at the weekend against the winner from the match between French 15th seed Alize Cornet and Daniela Hantuchova.

Safina credited a year's work with her coach and an emphasis on fitness with helping her game rise to the occasion after collecting four titles in 2008 and losing to Ana Ivanovic in the Roland Garros final.

"I have a condition coach travelling with me, so day by day, the same person works on me," she said. "On the tennis court, it's the same. That's why I think you never see me taped." (dpa)