Australian Open, Melbourne
Venue: Melbourne Park Dates: 17-30 January
Coverage: Watch on BBC TV, Red Button, BBC Sport website (UK only) & Eurosport; listen on BBC 5 live sports extra and online; text commentary online;
Nadal currently holds the French Open, Wimbledon and US Open titles
World number one Rafael Nadal marched through to round two of the Australian Open after Brazilian opponent Marcos Daniel retired while trailing 6-0 5-0.
Nadal is aiming to become the first man since Rod Laver in 1969 to hold all four Grand Slams at once.
Juan Martin del Potro marked his first Grand Slam appearance in a year with a straight sets victory over Dudi Sela.
David Nalbandian outlasted fellow veteran and home favourite Lleyton Hewitt in a five-set thriller.
The Argentine player, the 27th seed this year, had to save two match points but eventually triumphed 3-6 6-4 3-6 7-6 (7-1) 9-7 in a match that lasted four hours and 47 minutes and included a 93-minute final set.
Hewitt came into the match leading 3-2 in their meetings, including wins in the 2002 Wimbledon final and a controversial quarter-final match in 2005. But it was Nalbandian who sealed the win with a perfect lob on his first match point.
Nalbandian seals epic over Hewitt
It was Hewitt's fifth first-round exit at his record 15th consecutive Australian Open and a bitter outcome after suffering a hip injury in last year's fourth round loss to eventual champion Roger Federer.
He had 30 break point opportunities but only managed to break seven times while Nalbandian managed six from 12.
But the winner, who will face Richard Berankis of Lithuania in the second round, paid tribute to his Australian rival.
"He played unbelievable. From the beginning it was very tough. A very tough first round match," said Nalbandian.
"I expected a match like that with the crowd. It's amazing playing with full stadium, with him here in Australia.
"I think we both had a lot of chances. I mean, I was two match points down and then I was serving for the match before in the fifth.
"It was that kind of match that nobody will forget it."
Earlier in the day, Nadal's 47-minute victory was all too easy, with world number 93 Daniel seemingly lacking in form and fitness from the outset.
The top seed will know tougher tests lie ahead but looked sharp in the short time he was on court and next plays American qualifier Ryan Sweeting.
After breaking serve in the opening game, Nadal immediately found rhythm on his own serve and then broke again for a 3-0 lead.
Daniel was struggling to get close to the 24-year-old's groundstrokes and Nadal broke to love in game five before serving out the opening set.
The Brazilian underdog appeared to jar his heavily-strapped knee in dropping serve again at the beginning of the second set.
A short delay ensued and it looked to have affected Nadal's concentration as Daniel registered four break points in game two.
But the nine-time Grand Slam winner held firm and had broken serve twice more by the time Daniel, who took a medical timeout and then required a second visit from the trainer, called it a day.
"It's terrible feeling," said Nadal, who
retired with a knee injury during his Australian Open quarter-final against Andy Murray
It's difficult to say I played really well or I played bad. I think I played alright
"I wish him all best and a fast recovery. You don't want to retire but finally it's better because if it's bad you want to go and recover.
"It's difficult when you have to go out of a big tournament like the Australian Open. To go out like that was really tough for me mentally."
Reflecting on 2010, Nadal was particularly pleased with the way in which he recovered from knee trouble to win the French Open, Wimbledon and a maiden US Open title.
"Last year was probably the most emotional season of my life," he admitted. "I came back after a difficult situation, won at Roland Garros and the US Open was really special.
"It's difficult to say I played really well or I played bad.
"I think I played alright. I played some good shots, some long shots. The serve can be a little bit better.
Yeah, that's the only point that I think I can improve."
Elsewhere, Del Potro played his first Grand Slam match a fourth-round exit at Melbourne Park in 2010.
And the Argentine, who won the 2009 US Open, looked to have put his wrist injury behind him as he overcame Israel's Sela 7-6 (15-13) 6-4 6-4.
"I feel good with my wrist," he said. "I need time, I need matches, I need sets, I need hours on the court. Then in the future, I will be better."
The win keeps Del Potro on course for a last 16 meeting with world number five Murray, who
advanced after opponent Karol Beck retired while trailing 6-3 6-1 4-2.
Fourth seed Robin Soderling was a comfortable 6-4 6-2 6-2 winner against Italy's Potito Starace and next up for the Swede is Gilles Muller.
"Winning in straight sets, it's a very good start," said Soderling.
Soderling was delighted with his straight-sets victory
"I struggled a little bit in the first set but I think after that I played better and better. At the end, I played pretty good.
"I haven't had much success here in the past. That's why, you know, it's even more important to really focus on the next match all the time.
"Now I got past the first round and I have a difficult match coming up and I have to play well.
The seventh seed David Ferrer overcame a mid-match wobble to beat Jarkko Nieminen 6-4 6-3 1-6 6-2, while 13th seed Jo-Wilfried Tsonga, who lost in the 2008 final to Novak Djokovic, came back from two sets down to beat Philipp Petzschner of Germany 4-6 2-6 6-2 6-3 6-4.
Number 15 seed Marin Cilic, beaten by Murray in the semi-finals last year, eased past Donald Young and 20th seed John Isner sent down 26 aces en route to victory over Florent Serra.
The 21st seed Marcos Baghdatis, the 2006 runner-up, needed five sets before defeating Slovenia's Grega Zemlja 3-6 7-5 6-1 4-6 6-2.
Feliciano Lopez, seeded 31st, saw off Alejandro Falla, who took Roger Federer the distance in round one of Wimbledon, and he next plays Bernard Tomic.
The 18-year-old Australian wildcard claimed a 6-3 6-2 7-6 (7-5) victory over world number 44 Jeremy Chardy, to the home crowd's delight on Hisense Arena.