Australia Open PHOTOS: Sharapova falls to Cibulkova; Azarenka, Nadal advance

Third seed Maria Sharapova was dumped out of the Australian Open on Monday with a 3-6, 6-4, 6-1 fourth round loss to Slovakia's Dominika Cibulkova on Rod Laver Arena.

The 2008 champion had to take a medical time-out between the second and third sets for treatment on an undisclosed injury. She was grimacing when bending over and grabbing her lower back during the final set.

Sharapova's demise comes a day after Serbia's Ana Ivanovic beat world number one and title favourite Serena Williams, also in the fourth round.

"I watched that match, it was a great match for Ana, but this was a little bit of a different story," Cibulkova said in a courtside interview.

"The most important thing was that I went on the court and I was 100 per cent sure I could win this match. I wasn't doubting myself."

Sharapova took the first set 6-3 as both players struggled with their serve, but Cibulkova won the second after racing to a 5-0 lead, which the Russian pegged back, before the diminutive Slovak finally held serve to send the match to a decider.

Sharapova then took the medical time-out but was unable to halt Cibulkova's momentum as the Slovak raced through to win the set and reach her first Australian Open quarter-final.

She will meet either eighth-seed Jelena Jankovic or 11th-seeded Romanian Simona Halep for a place in the last four.

"I just kept going. I knew what I had to do and I was doing exactly the right things," Cibulkova added.

"The most important thing is to believe in yourself."

Victoria Azarenka stayed on track for a third consecutive Australian Open title with a composed 6-3, 6-2 victory over 13th-seed Sloane Stephens in the fourth round on Monday.

With third seed Maria Sharapova and World No 1 Serena Williams both losing in the fourth round, Azarenka has firmed as favourite to retain her crown and become the first woman to win three successive Melbourne Park titles since Martina Hingis (1997-99).

Azarenka and Stephens had played a controversial match in the semi-finals last year and their clash on Monday had the potential for more when Stephens blasted a shot back at Azarenka that hit her in the upper thigh in the first set.

The Belarusian appeared to ignore Stephens' apology and repaid the American with a similar shot shortly afterwards.

Azarenka then controlled the match from the baseline and waited for the 20-year-old to make errors, wrapping up the win in 91 minutes.

A ruffled Rafael Nadal fumed at the chair umpire after being called for multiple time violations on serve but composed himself to fend off a gallant Kei Nishikori and reach the quarter-finals of the Australian Open on Monday.

Top seed Nadal had come hurtling into the match with a brutal demolition of Gael Monfils, but encountered a far different beast in 16th seeded Japanese, who broke his serve for the first time in the tournament and rattled the Spaniard in a 7-6 (7-3), 7-5, 7-6 (7-3) loss at Rod Laver Arena.

Battling fatigue, the impressive Nishikori rallied from 4-1 down to serve for the third set but Nadal broke back to force the high-quality clash into a second tense tiebreak.

The weary Nishikori belted a shot long to give Nadal three match points and the Spaniard sealed it on the first to set up a quarter-final with 22nd seed Grigor Dimitrov.

Andy Murray smashed a racket in a rare display of frustration after being taken to a fourth set before reaching the quarter-finals of the Australian Open with a 6-1, 6-2, 6-7 (6), 6-2 victory over lucky loser Stephane Robert on Monday.

After racing through the first two sets in just over an hour, Wimbledon champion Murray blew a couple of match points in the third and was dragged into a tiebreak by the 33-year-old Frenchman, who won it 8-6.

It was the first set fourth seed Murray had lost in the tournament but, after a change of shirt, he whipped through the fourth set in 28 minutes to seal a quarter-final date against either Roger Federer or Jo-Wilfried Tsonga.

Robert was the first lucky loser to reach the fourth round at MelbournePark and had won just four main draw matches in 10 previous grand slam appearances.

The world's top-ranked doubles pair, Bob and Mike Bryan, suffered their earliest Australian Open exit in more than a decade on Monday when they lost 7-6(9), 6-4 to American Eric Butorac and South Africa's Raven Klaasen in the third round.

The American twins, who have won the title six times, led 4-0 in the first-set tiebreak before being overhauled and were then broken once in the second set.

"It's frustrating, we like coming down here and starting the year hot," Mike Bryan told reporters.

"I don't think we played terribly, just the margins are really small. We're a front-running team and (if we won the tiebreak) we probably win that in straight sets but all credit goes to those guys, they served tough."

The last time the twins exited Melbourne so early was in 2003, again in the third round.

"I think it's the first time we've lost in straight sets since June 2012," said Bob Bryan.