Rafa Nadal pummelled Croatia's Marin Cilic into submission with a brutish 6-2, 6-4, 6-3 victory to reach the Australian Open quarter-finals on Monday.

Nadal's win under the Melbourne floodlights kept alive the world number one's bid to become only the third man, and first since 1969, to hold all four grand slam titles at once.

It also wiped away any lingering concerns about the flu bug that took the edge off his game in the first week and caused him to pour with sweat against Bernard Tomic on Saturday.

"Before the match I was scared, seriously," Nadal told reporters after setting up a clash with fellow Spaniard David Ferrer, the seventh seed.

"Scared in a good way. But I played my best match here by far.

"I didn't sweat as much today," added Nadal, who shed two and a half kilos in his previous win over Australian teenager Tomic.

"Before I was sweating like crazy and it was a night session. Tonight I was able to play with high intensity, more inside the court and more aggressive."

Ukrainian Alexandr Dolgopolov produced a stunning five-set upset over fourth seed Robin Soderling to reach the Australian Open quarter-finals on Monday.

The pony-tailed Dolgopolov completed a shock 1-6, 6-3, 6-1, 4-6, 6-2 win in Melbourne with a heavily whipped forehand to become only the second man from his country to reach the last eight of a grand slam.

Swede Soderling, French Open runner-up the past two years, took a medical timeout in the fourth set to treat blisters on his foot before going on to level a cliff-hanger fourth round match.

However, he was quickly staring down the barrel in the deciding set, Dolgopolov drilling another big forehand past the Swede to break for 3-1.

The 23-year-old was making only his fourth grand slam appearance but held his nerve to record his first win over a top 10 player and the biggest upset of the year's first major so far.

In-form Czech Petra Kvitova battled her way out of an early-match malaise before grinding down Italian Flavia Pennetta 3-6, 6-3, 6-3 to make her first quarter-final.

The 25th-seeded Kvitova muttered to herself in irritation as her baseline rockets mis-fired early, but was yelping in triumph after finding her line to close out the match in 115 minutes.

Twenty-year-old Kvitova, a surprise semi-finalist at Wimbledon last year, returned fiercely in the final two sets and captured the decisive break at 3-3 in the third when Pennetta netted a shot under withering pressure.

Pennetta saved one match point at 5-3, but netted a backhand on the second to give the rangy Kvitova her ninth consecutive win.

Kvitova will play Vera Zvonareva in the last eight.

A red-hot Andy Murray destroyed Austria's Juergen Melzer 6-3, 6-1, 6-1 to reach the Australian Open quarter-finals on Monday, firing an emphatic title warning with a performance of pure class.

The Briton, who lost to Roger Federer in last year's Melbourne final, produced arguably the best tennis of the tournament so far to see off Melzer in an hour and 44 minutes.

Fifth seed Murray had Melzer screaming furiously at himself, the 11th seed hurling his racquet to the court as the Scot powered into a two-set lead.

Murray capped an awesome display on a sun-baked Rod Laver Arena with his 13th ace to suggest he can finally end his wait for a first grand slam title.

Patient Spaniard David Ferrer ended the run of giant-killing qualifier Milos Raonic to advance to the quarter-finals of the Australian Open with a 4-6, 6-2, 6-3, 6-4 victory on Monday.

The seventh-seeded Ferrer blunted the Canadian's rocket serves with nippy returns and unleashed some sweetly-struck passing shots to wrap up the match in 156 minutes at a sun-drenched Rod Laver Arena.

The 20-year-old Raonic, who blasted 31 aces in his third-round victory over 10th seeded Russian Mikhail Youzhny, could not repeat the fireworks, and ended up conceding the match clubbing a forehand wide, his 68th unforced error.

Ferrer will play the winner of Croatia's Marin Cilic or fellow Spaniard Rafa Nadal, who is bidding for a fourth consecutive Grand Slam.

Patient Spaniard David Ferrer ended the run of giant-killing qualifier Milos Raonic to advance to the quarter-finals of the Australian Open with a 4-6, 6-2, 6-3, 6-4 victory on Monday.

The seventh-seeded Ferrer blunted the Canadian's rocket serves with nippy returns and unleashed some sweetly-struck passing shots to wrap up the match in 156 minutes at a sun-drenched Rod Laver Arena.

The 20-year-old Raonic, who blasted 31 aces in his third-round victory over 10th seeded Russian Mikhail Youzhny, could not repeat the fireworks, and ended up conceding the match clubbing a forehand wide, his 68th unforced error.

Ferrer will play the winner of Croatia's Marin Cilic or fellow Spaniard Rafa Nadal, who is bidding for a fourth consecutive Grand Slam.