Nadal cruised past countryman Feliciano Lopez on Sunday, winning 6-4, 6-4, 6-2 to reach the quarter-finals of the Australian Open.
Nadal, who hurt his knee while sitting in a chair the day before the tournament began, is one win away from a possible semifinal against old rival Roger Federer after beating his fellow Spaniard for the ninth time in 11 matches.
On a sunny day with the temperature rising to 31 degrees, both players sat with ice towels around their necks during the changeovers.
Nadal needed treatment from the trainer for a left ankle problem after three games of the first set. By that time, he had already broken serve.
It was more of the same the next two sets as Nadal maintained control against his "very good friend" Lopez.
"I am fine," Nadal said. "It was a very, very hot day. I think it's positive to keep winning in straight sets."
Federer was up against 19-year-old Australian Bernard Tomic in the first match of the night session later Sunday. The 16-time Grand Slam champion hasn't lost to a teenager since 2006 against Andy Murray at the Cincinnati Masters.
In men's doubles action, second seeds Daniel Nestor of Toronto and Max Mirnyi of Belarus beat Italy's Daniele Bracciale and Potito Starace 7-6 (7), 6-2 to earn a quarter-final spot.
Also Sunday, defending champion Kim Clijsters was to face Li Na in a repeat of the 2011 final. Clijsters beat Li 3-6, 6-3, 6-3 to win her fourth major title a year ago.
Victoria Azarenka was the first player to reach the quarter-finals when she beat Iveta Benesova 6-2, 6-2.
The third-seeded Belarusian is yet to drop a set at the tournament and will next meet eighth-seeded Agnieszka Radwanska, who beat Julia Goerges of Germany 6-1, 6-1.
With the win, 22-year-old Azarenka stayed in the hunt for the No. 1 ranking. Petra Kvitova and Maria Sharapova can also claim the top spot from Caroline Wozniacki.
"I would be a liar if I said I didn't care about it," Azarenka said. "It's in the back of my head and we'll take it day by day, I guess."
Azarenka, like Wozniacki, is aiming for her first Grand Slam title. She has never gone past the quarter-finals at the Australian Open, but is 6-3 against Radwanska. The last of those victories came at the Sydney International, which Azarenka won before coming to Melbourne.
Sunday's win was her ninth straight, but the likes of Serena Williams and Clijsters are still attracting more attention.
"For me, doesn't really matter. I try to focus on myself," Azarenka said. "I think I'm in the best shape physically right now, so it kind of helps other aspects of the game. I feel pretty good out there."
Williams routed Greta Arn 6-1, 6-1 on Saturday for her 17th straight win at the Australian Open.
Coming off an injury-ravaged 18 months, Williams is seeded 12th in Melbourne. She hasn't held the top ranking since 2010, the year she won the last of her 13 Grand Slam titles.
On Saturday, she spoke expansively about her off-court activities: She's taking courses in kinesiology and management and preparing for an appearance in a "pretty big" TV show.
Yet Arn says "everybody knows" if Williams hits top form she will win the Australian Open, where she hasn't lost since 2008. She won back-to-back titles in 2009 and 2010 and was unable to defend her title last year while she recovered from two foot surgeries.
Next up for Williams is unseeded Russian Ekaterina Makarova. After that, things are likely to get a lot tougher. Sharapova is a potential quarter-final opponent, and Wimbledon champion Kvitova may await in the semifinals.
"I'm nowhere near where I want to be," said Williams, who came into the tournament nursing a sprained left ankle. "I'm just trying to play through it. A little rusty, just trying to play through my rust."
Sharapova and Kvitova joined Williams in advancing to the fourth round on Saturday. Between the three of them, they lost six games.
Kvitova was leading 6-0, 1-0 when Russian opponent Maria Kirilenko retired. Sharapova, who won her first two matches 6-0, 6-1, was tested for the first time and still came out with a 6-1, 6-2 win over U.S. Open semifinalist Angelique Kerber.
It was a day of lopsided scorelines on Rod Laver Arena.
No. 1-ranked Novak Djokovic routed Nicolas Mahut 6-0, 6-1, 6-1 in one hour 14 minutes to give the Frenchman a lousy 30th birthday present.
Mahut, who lost the longest Grand Slam match in history at 11 hours five minutes at Wimbledon in 2010, was hampered by a left leg injury, but said he played on because the previous matches on Rod Laver Arena were over so quickly.
"I wish him happy birthday and hopefully tonight he can enjoy it," Djokovic said.
The defending champion has won 24 straight sets at the Australian Open, and has lost 10 games in his first three matches this time.
Djokovic likely gets an evening slot for his fourth-round match against Lleyton Hewitt. The 30-year-old Australian downed promising Milos Raonic of Thornhill, Ont., 4-6, 6-3, 7-6 (5), 6-3 in Saturday's final match of the day before a raucous home crowd.
No. 4-ranked Murray, beaten in the last two Australian finals, brushed aside Michael Llodra 6-4, 6-2, 6-0 Saturday to leave France with two players in the draw, having started the day with six.
Jo-Wilfried Tsonga was the other Frenchman to advance and next plays Kei Nishikori, the first Japanese man to reach the fourth round in Melbourne in the Open era.