Melbourne:Defending champion Amelie Mauresmo and No 3 Svetlana Kuznetsova dropped out in shocking upsets on Sunday, clearing the way for Serena Williams to make an unlikely run to the Australian Open final. Seven-time Grand Slam champion Williams, who missed most of last season with a knee injury, showed glimpses of her peak form in a 6-3, 6-2 win over 11th-seeded Jelena Jankovic. "It was absolutely sensational ... I just play some of my best tennis here," said Williams, who had 31 winners and dropped serve only once. "I'm on the right track - I like being a dangerous floatie." Sixth-seeded Andy Roddick beat No 9 Mario Ancic 6-3, 3-6, 6-1, 5-7, 6-4 to set up a men's quarterfinal against old friend and housemate Mardy Fish. "I felt like at end of fourth set he had the momentum and was really being offensive in the points," Roddick said. "I knew that in fifth set, win or lose, I had to turn the tables on the aggression. I was lucky to get through." The second-seeded Mauresmo dropped a 6-4, 6-3 decision to 70th-ranked Lucie Safarova, and Kuznetsova fell 6-4, 6-2 to Shahar Peer of Israel in the women's fourth round. Peer made the quarterfinals at a major for the first time and faces one of the best in the game. Williams covered the court with ease against Jankovic, despite question marks over her fitness. She won the last of her majors here in 2005. And Jankovic was in form, coming to Melbourne with a title at Auckland and a run to the final at last week's Sydney International. Fish in quarters The unseeded Fish also made the last eight for the first time at a Grand Slam, beating No 16 David Ferrer 6-1, 7-6 (4), 2-6, 7-5. Fish lived with Roddick and his family for a year in 1999 and said the pair were like brothers. In a post-match interview with former No 1 Jim Courier, Roddick joked that Fish could repay the rent by losing the quarterfinal. "I have a hard time thinking he's going to agree with it, but heck, I might as well propose it," Roddick said. Mauresmo was up a service break early before slumping against Safarova, a 19-year-old Czech player who had only won one match in six previous Grand Slam tournaments. "It's amazing. I still can't believe it," Safarova said. "I'm so happy. It's incredible." It was Safarova's first time on center court at the Australian Open and her first match against Mauresmo. "I came out this morning and said, 'Wow this is a big court.' But I felt really comfortable here," Safarova said. She next plays fellow Czech Nicole Vaidisova, who beat seventh-seeded Elena Dementieva 6-3, 6-3. Safarova acknowledged her boyfriend - 13th-seeded Tomas Berdych - who beat Dmitry Tursunov 6-2, 6-1, 6-1 in a rain-delayed third-round match. Mauresmo had her Grand Slam breakthrough last year in Melbourne, winning her first major title seven years after reaching her first final, also in the Australian Open. The 27-year-old Frenchwoman added the Wimbledon title and spent most of 2006 ranked No 1. In third-round matches delayed until Sunday by heavy rain, China's Li Na upset No. 9 Dinara Safina 6-2, 6-2, 12th-seeded Anna Chakvetadze beat Jelena Kostanic Tosic 6-4, 6-4, and No. 15 Daniela Hantuchova edged Ashley Harkleroad 6-7 (6), 7-5, 6-3. On the men's side, No 12 Tommy Haas beat fellow German Florian Mayer 7-6 (3), 6-3, 6-3. Safarova nails Mauresmo Mauresmo looked to be in good shape after an early break. But the left-handed Safarova, her right thigh heavily taped, quickly reversed roles and soon was hitting like the favorite. She had Mauresmo running and lunging all over the court, nailed crisp volleys and passed the Frenchwoman seemingly at ease. Mauresmo, her confidence clearly waning, was shouting at herself as her mistakes piled up. It looked as if nerves might get to Safarova as the pressure ratcheted up at 4-4 in the first set. She completely missed a backhand as Mauresmo was serving to make it 30-30. But Mauresmo returned the favor, double-faulting to set up a break point, then netting a backhand. Safarova had no nerves in finishing off the set, hitting a clean forehand winner down the line that Mauresmo could only watch. The crowd seemed stunned as Safarova got two quick breaks in the second set and served at 4-1. Mauresmo, shaking her head in disbelief, got one break back, then held to pull to 4-3, getting a pair of aces when she successfully challenged line calls. But after fending off two match points, she netted a shot to surrender the match. Mauresmo quickly piled her gear into her bag, threw a towel over her shoulder and walked off, waving to the crowd. She went directly to warm up for a doubles match. Kuznetsova, troubled recently by a respiratory problem that forced her out of a warmup tournament, dropped serve five times against the 16th-seeded Peer, who spends time in her offseason fulfilling mandatory military service in the Israeli army. "I feel like I'm on a soccer field," Peer said of the noisy crowd. "It will be the first time for me to get to a quarterfinal in a Grand Slam, so I had nothing to lose."