- World No. 2 Rafael Nadal reaches third round in Melbourne, beating Tommy Haas
- Third seed Roger Federer also into last 32 after his opponent pulls out with injury
- American eighth seed Mardy Fish crashes out of season's opening grand slam
- No. 7 Tomas Berdych and No. 11 Juan Martin del Potro go through with victories
Rafael Nadal and Roger Federer remained on course for a semifinal showdown at the Australian Open with untroubled passage to the third round on Wednesday, but top American hope Mardy Fish became the first high-profile casualty of the men's draw.
Second seed Nadal won in straight sets for the second match in a row, beating former world No. 2 Tommy Haas, while Federer had a walkover against another German, Andreas Beck.
Nadal showed no signs of the recurring knee problem that troubled him before Monday's opening win as he triumphed 6-4 6-3 6-4 against the oldest player in the singles draw.
The 33-year-old Haas has reached the semifinals three times in Melbourne, but has fallen to 190th in the rankings after a series of injury problems.
"I really practiced well," said Nadal, who next faces Slovakia's world No. 119 Lukas Lacko -- a four-set conqueror of American Donald Young.
"I had very good preparation. I won already two matches in straight sets with positive feeling. I am well."
Federer, seeking his fifth title in the season's opening grand slam and his 17th overall, will face big-serving Croatian Ivo Karlovic in the last 32 following Beck's pre-match withdrawal with a back injury.
The Swiss third seed, whose last major title came in Australia in 2010, had been due to play away from the main Rod Laver Arena court for the first time in 52 matches.
But he said he was pleased that women players were getting more of a chance to play in marquee night matches this year, which means fewer late finishes for the men.
"I don't think it's good that they always had the women's match first. I think it's good to mix it up," the 30-year-old said.
Eighth seed Fish was less happy to play in the scorching afternoon heat, complaining about the timeouts that Colombian opponent Alejandro Falla took for treating cramps before sealing a 7-6 (7-4) 6-3 7-6 (8-6) victory.
"I thought he was having some physical issues. But then in between, on every point, he was totally fine," Fish said.
"I have a hard time calling the trainer for anything. I wouldn't want the other guy to know that I was hurting in the first place. To be able to get help for lack of fitness ... I mean, if you saw how much water I drank in the past three days just to hydrate to make sure that something like that didn't happen -- I did all the right things there."
Falla, ranked 71st, will next play Germany's Philipp Kohlschreiber, with the winner of that match likely to take on Argentine 11th seed Juan Martin del Potro.
The 2009 U.S. Open champion set up a third-round clash with Taiwan's world No. 79 Yen-Hsun Lu by beating Slovenia's Blaz Kavcic 6-4 7-5 6-3, continuing his career revival following longterm wrist injury.
Czech seventh seed Tomas Berdych went through after beating Belgium's Olivier Rochus in straight sets, and will next play big-serving South African No. 30 Kevin Anderson.
American 16th seed John Isner survived another marathon match as he defeated 2006 semifinalist David Nalbandian 4-6 6-3 2-6 7-6 (7-5) 10-8.
The match lasted more than four and a half hours, and the deciding set went for 99 minutes -- with Nalbandian furious that he was denied a video challenge at 8-8 when he held a break-point on Isner's serve.
"Obviously the ump didn't think he challenged in time, but maybe because of the crowd noise the ump couldn't hear it or what not," Isner said. "The break went in my favour, for sure."
Isner, who was involved in the longest match in tennis history at Wimbledon in 2010, won the game and then broke the Argentine's serve in the next to set up a clash with Spanish 18th seed Feliciano Lopez.
His fellow American Sam Querrey lost to Australia's 19-year-old rising star Bernard Tomic, who will next face Ukrainian 13th seed Alexandr Dolgopolov.
Spanish 10th seed Nicolas Almagro came from 2-1 down to beat Bulgaria's Grigor Dimitrov in five sets to book a tie with Swiss 21st seed Stanislas Wawrinka, who beat 2006 finalist Marcos Baghdatis of Cyprus, 7-6 6-4 5-7 6-1.