Williams advances to fourth round

MELBOURNE, Australia -- Serena Williams stayed on track for an improbable eighth Grand Slam singles title, beating fifth-seeded Nadia Petrova 1-6, 7-5, 6-3 on Friday to advance to the fourth round of the Australian Open.

Limited to four tournaments last year because of a chronic knee injury, the 2005 Australian Open champion dropped to 95th in the year-end rankings.

On the men's side, 14th-seeded Novak Djokovic beat Danai Udomchoke 6-3, 6-4, 5-7, 6-1 and will face the winner of the Roger Federer vs. Mikhail Youzhny match in the fourth round.

-- AP