Venue: Melbourne Park Date: 19 January-1 February
Coverage: BBC Red Button, Radio 5 Live sports extra, BBC Sport website (Red Button coverage streamed on website throughout fortnight)
Nadal is trying to win his first Grand Slam title on hard courts
World number one Rafael Nadal was in superb form as he saw off Fernando Gonzalez in straight sets to reach the last eight at the Australian Open.
The Spaniard followed up three straightforward wins with a 6-3 6-2 6-4 defeat of Chilean Gonzalez.
Nadal will play France's Gilles Simon in the quarters after injury forced Gael Monfils to retire in their match.
Jo-Wilfried Tsonga beat James Blake 6-4 6-4 7-6 (7-3) and will meet Andy Murray's conqueror Fernando Verdasco.
Simon, the sixth seed, was leading 6-4 2-6 6-1 when compatriot Monfils quit with a wrist injury.
Tsonga, the 2008 finalist, was in impressive form in Monday's night match as he cruised past American Blake in two hours and 23 minutes.
Nadal (1) v Simon (6)
Verdasco (14) v Tsonga (5)
Roddick (7) v Djokovic (3)
Del Potro (8) v Federer (2)
It means the 23-year-old Frenchman stays on track for a repeat of last year's explosive semi-final against Nadal.
World number one Nadal dominated his fourth-round match from the outset, only slipping up at the start of the third set by dropping serve but quickly making amends.
"Today I think I played well," he said. "Very solid match from the baseline.
"Playing very good forehands, backhands. Maybe the only thing today I can improve a little bit more for sure is the serve.
"Today I was not 100% happy with my serve. Wasn't very bad, but I think I was serving better the last matches."
Tsonga was at his brutal best as he dispatched ninth seed Blake in straight sets.
The Frenchman broke serve in the opening game of the first two sets before holding serve comfortably to leave Blake facing a monumental task.
Following a 15-minute break for the Australia Day fireworks, Blake came out and broke serve for the first time and had two set points to take the match into a fourth set.
But Tsonga broke back with an outrageous, dipping forehand into the corner and then dominated the tie-break against a fast-fading Blake.
"I think I'm playing better than last year," said Tsonga, who lost to Novak Djokovic in the 2008 final after destroying Nadal in the last four.
"I'm stronger maybe in my head, and it helps a lot."
Sixth seed Simon is into his first Grand Slam quarter-final but was reluctant to celebrate given the manner of his victory over one of his closest friends on the tour.
"It is very hard, because we are very close," said Simon afterwards. "I did not want to win like this."
Both players had made an error-strewn start to the match with the bright sun on the Rod Laver Arena causing them problems on serve.
Monfils, in particular, had struggled - being broken three times and facing break points in every one of his service games in the first set.
But he responded with some breathtaking tennis to take the second set before breaking down in the third set.
Monfils took a medical time-out at 1-4 before being broken again as Simon took the third set and he was clearly in trouble.
The 22-year-old walked to the net soon after the start of the fourth set and, after telling Simon he could not continue, the pair embraced.