By JOHN PYE
AP Sports Writer
MELBOURNE, Australia -- Olympic silver medalist Dinara Safina reached the fourth round for the first time in seven trips to the Australian Open with a 6-2, 6-2 win over Kaia Kanepi of Estonia on Friday.
The 22-year-old Russian, who broke into the top 10 for the first time last year, took 4-1 leads in each set and ousted the 25th-seeded Kanepi in 66 minutes.
Third-seeded Safina is yet to win a Grand Slam singles title, although she reached the final at the French Open last year before losing to Ana Ivanovic of Serbia.
She also lost the Olympic gold medal match to fellow Russian Elena Dementieva -- an outcome repeated last week in the Sydney International final.
Fellow Russian Nadia Petrova, seeded 10th, advanced when Kazakhstan's Galina Voskoboeva retired with back pain after losing the first set 6-1.
Safina's older brother, Marat Safin, looms as an obstacle to second-ranked Roger Federer's quest to equal Pete Sampras' 14 Grand Slam singles titles when they meet later Friday.
Safin beat Federer in the semifinals here four years ago before going on to claim the 2005 Australian Open title.
In the biggest upset so far at the season's first major, sixth-seeded Venus Williams lost 2-6, 6-3, 7-5 on Thursday night in the second round to Carla Suarez Navarro, a 20-year-old Spaniard ranked No. 46.
"She was super consistent and aggressive and just went for her shots," said Williams, the reigning Wimbledon champion. "I wasn't in control of the points."
Williams was broken while serving for the match and dropped the last five games.
It means there will be no Williams vs. Williams showdown in the semifinals. Second-seeded Serena Williams did her part, advancing 6-3, 7-5 over Argentina's Gisela Dulko. But she was far from happy, either, giving herself a "D-minus at best" for her form.
Suarez Navarro reached the French Open quarterfinals last year as a qualifier, beating 2006 Australian Open and Wimbledon champion Amelie Mauresmo before losing to runner-up Jelena Jankovic.
"You must be aggressive during all the match because, if not, she's going to take control of you," Suarez Navarro said of her biggest win so far in four Grand Slams.