Seeded male players breezed through the fourth round of the Australian Open, while top-ranked Caroline Wozniacki aimed to cap her first Grand Slam championship after a comfortable third-round victory in Melbourne.

Rafael Nadal of Spain picked up a 6-2, 6-4, 6-2 win over Slovakian Lukas Lacko at Rod Laver Arena to reach the fourth round without dropping a set at Melbourne Park.

World number-two Nadal finished the game with 27 winners and a first-serve percentage of 81, while unseeded Lacko made 30 double faults during the entire game.

Nadal's compatriot Feliciano Lopez dashed U.S. hopes by beating John Isner, the last remaining American male player at the Australian Open. Lopez clinched the intense five-set victory 6-3, 6-7 (3-7), 6-4, 6-7 (0-7), 6-1.

Four-time Australian Open winner Roger Federer appeared nervous at the beginning of his game against Croatian giant Ivo Karlovic on Friday. The Swiss player was put in an awkward situation as he could only wrap the first set 7-6 (8-6) as 208-centimeter Karlovic blocked the court with his oversized frame and aggressive serves. Nevertheless, Federer found his form to claim the following two sets 7-5, 6-3.

"I knew going in it was going to be tough," Federer said." I played him 10 times, and we've played some breakers. I knew it could come down to a few here and here. I definitely got a bit fortunate and started to play better as the match went on."

Elsewhere, Spain's Nicolas Almagro knocked Switzerland's Stanislas Warinka out in straight sets 7-6 (7-2), 6-2, 6-4, while Philipp Kohlschreiber of Germany crushed Colombia's Alejandro Falla 6-3, 6-2, 7-6 (7-3). Although South African's Kevin Anderson brought the game into tiebreakers twice, he still went down to last year's China Open champion Tomas Berdych 6-7 (5-7), 6-7 (1-7), 1-6.

On the women's side, world number-one Caroline Wozniacki came a step closer to her first Grand Slam title when she axed Romania's Monica Niculescu 6-2, 6-2. After her victory, Wozniacki defended her world top ranking against Victoria Azarenka, Petra Kvitova and Maria Sharapova, who could crown the number one spot at the end of the tournament.

"I've proven myself for the last two years," Wozniacki said as she talked about the number-one ranking. "I've finished number one twice in a row. For me, the most important thing is to keep improving. If I do that, I know I can play at a very high level."

Victoria Azarenka's temper flared during her game against Mona Barthel when the Belarusian called for a sideline contest on match point despite that she had run out of Hawk-Eye challenges. Azarenka eventually snatched a 6-2, 6-4 victory to earn a fourth-round game.

In additional, eighth-seeded Agnieszka Radwanska swept her opponent Galina Voskoboeva 6-2, 6-2. Jelena Jankovic won her match against Christina McHale 6-2, 6-0, while Julia Goerges made a comeback from a 3-6 first-set loss and eliminated Romina Oprandi 6-3, 6-1 in following sets.