MELBOURNE, Australia -- Roger Federer, trying to equal Pete Sampras' record 14 Grand Slam singles titles, had a narrow fourth-round win over Tomas Berdych on Sunday. On the court where women's No. 1 Jelena Jankovic was knocked out in the day's opening match and No. 3 Dinara Safina had to save match points before advancing, Federer also appeared in trouble. Not in his mind. "I wasn't thinking of losing, that's for sure," Federer said after reaching the quarterfinals with a 4-6, 6-7 (4), 6-4, 6-4, 6-2 win. "The finish line was still very far for Tomas. I knew that. "He pushed me to the limit. You've got to hang in there, there's no other solution." He next faces 20-year-old Juan Martin del Potro, seeded eighth from Argentina, who advanced 5-7, 6-4, 6-4, 6-2 over No. 19 Marin Cilic. Gilles Simon advanced to the Australian Open quarterfinals Monday when fellow Frenchman and longtime friend Gael Monfils retired after three sets. In the opening women's match, Carla Suarez Navarro reached the quarterfinals after a 6-3, 6-2 win over No. 21 Anabel Medina Garrigues in an all-Spanish match. Second-seeded Serena Williams, seeking a 10th Grand Slam singles title, was to play No. 13 Victoria Azarenka of Belarus at Rod Laver Arena. Defending champion Novak Djokovic of Serbia jumped to a 5-0 lead, then was pushed the rest of the way in a 6-1, 7-6 (1), 6-7 (5), 6-2 victory over 2006 runner-up Marcos Baghdatis of Cyprus in a match that finished at 2:26 a.m. Monday. He'll next play American Andy Roddick, who ousted No. 21 Tommy Robredo 7-5, 6-1, 6-3. The top eight seeds in the men's draw made it to the fourth round here for the first time since 1970. As well as No. 1 Nadal, No. 4 Andy Murray and No. 5 Jo-Wilfried Tsonga were in action later Monday. If the top eight reach the quarters, it will be a first in a Grand Slam in the Open era. The women's draw is quickly diminishing, with 2004 U.S. Open winner Svetlana Kuznetsova the only other major winner besides Williams remaining in the draw. While Jankovic was disappointing in a 6-1, 6-4 loss to 2007 Wimbledon finalist Marion Bartoli on Sunday, Jelena Dokic made a surprising run to the quarterfinals. Dokic, who won a wild-card tournament to get into her first main draw at a Grand Slam event in three years and was ranked No. 187 last week, had a 7-5, 5 -7, 8-6 fourth-round win over Russia's Alisa Kleybanova. "To be in the quarterfinal of a Grand Slam is just amazing," said Dokic, a former world No. 4 and 2000 Wimbledon semifinalist. She next plays Safina, who faced match points with No. 15 Alize Cornet serving at 5-3 in the deciding set but rallied to win 6-2, 2-6, 7-5.