Slovakia's Dominika Cibulkova knocked out World No.3 Maria Sharapova from the Australia Open here Monday while Rafael Nadal, Roger Federer and Andy Murray marched into the men's singles quarterfinals.
Sharapova is the second big upset in women's singles draw after World No.1 Serena Williams was beaten by Serbia's Ana Ivanovic Sunday.
Cibulkova fought back to beat Sharapova 3-6, 6-4, 6-1 in the fourth round at Melbourne Park.
Defending champion Victoria Azarenka, who breezed past America's Sloane Stephens 6-3, 6-2 and will face next the winner between Agnieszka Radwanska and Garbine Muguruza, is now viewed as the favourite for the women's title.
China's Li Na, seeded fourth and a twice runner-up in the last three years, is regarded as a potential challenger.
Sharapova's loss continued her poor run since she lost to Williams in the French Open final last year. She was bundled out in the second round at Wimbledon and withdrew from the US Open with a shoulder injury.
Sharapova saved Cibulkova's first match point with a net cord that was shown by video review to have clipped the line.
She pushed a backhand wide on the second match point to lose in two hours and 12 minutes.
Cibulkova will meet Romania's Simona Halep, who eliminated Serbia's Jelena Jankovic 6-4, 2-6, 6-0, in the quarterfinals.
"The most important thing was that I went on the court 100 percent believing I could win," Cibulkova said.
"I kept going. I've beaten Maria before in the grand slams and the most important thing is to believe in yourself."
The Romanian complained about Sharapova's toss of ball.
"When the match was coming to the end, I was getting like a little bit angry about that (ball toss). I was keep talking to myself, why is she doing that? I thought it was on purpose."
In the men's singles, sixth seed Federer packed off Jo-Wilfried Tsonga 6-3, 7-5, 6-4 in one hour and 52 minutes, reaching the quarterfinals in Melbourne for the 11th consecutive year.
The Swiss showed his class against a tought opponent, setting up a quarterfinal meeting with Andy Murray, who needed four sets to dispatch lucky loser Stephane Robert of France 6-1, 6-2, 6-7 (6-8), 6-2 in two hours and 42 minutes.
Despite beating Federer at Roland Garros last year, Tsonga couldn't get close to the 17-time grand slam champion who produced his most impressive showing of the championship and provided evidence he can be a threat to the likes of Nadal, Murray and Djokovic.
"It's been a different type of tournament," said Federer. "It's been fun, it's been a good ride. I thought I played really well tonight. You've got to bring your best game (against Tsonga), because he dictates play a lot. I think I did a good job dictating play."
Nadal made through to the quarterfinal overcoming 16th seed Kei Nishikori 7-6 (7-3), 7-5, 7-6 (7-3). He next faces Grigor Dimitrov of Bulgaria.
Nishikori was in fine form but the powerful Spaniard was too much for the Japanese, eventually taking a long and tough three-setter which lasted over three hours.
Dimitrov, the 22-year-old 22nd seed, showed character beyond his years to overcome the unseeded Spaniard Bautista-Agut 6-3, 3-6 ,6-2, 6-4 in two hours and 24 minutes.
Dimitrov's serve was a major asset, slamming 11 aces with the fastest at 219kph.
Sharapova is the second big upset in women's singles draw after World No.1 Serena Williams was beaten by Serbia's Ana Ivanovic Sunday.
Cibulkova fought back to beat Sharapova 3-6, 6-4, 6-1 in the fourth round at Melbourne Park.
Defending champion Victoria Azarenka, who breezed past America's Sloane Stephens 6-3, 6-2 and will face next the winner between Agnieszka Radwanska and Garbine Muguruza, is now viewed as the favourite for the women's title.
China's Li Na, seeded fourth and a twice runner-up in the last three years, is regarded as a potential challenger.
Sharapova's loss continued her poor run since she lost to Williams in the French Open final last year. She was bundled out in the second round at Wimbledon and withdrew from the US Open with a shoulder injury.
Sharapova saved Cibulkova's first match point with a net cord that was shown by video review to have clipped the line.
She pushed a backhand wide on the second match point to lose in two hours and 12 minutes.
Cibulkova will meet Romania's Simona Halep, who eliminated Serbia's Jelena Jankovic 6-4, 2-6, 6-0, in the quarterfinals.
"The most important thing was that I went on the court 100 percent believing I could win," Cibulkova said.
"I kept going. I've beaten Maria before in the grand slams and the most important thing is to believe in yourself."
The Romanian complained about Sharapova's toss of ball.
"When the match was coming to the end, I was getting like a little bit angry about that (ball toss). I was keep talking to myself, why is she doing that? I thought it was on purpose."
In the men's singles, sixth seed Federer packed off Jo-Wilfried Tsonga 6-3, 7-5, 6-4 in one hour and 52 minutes, reaching the quarterfinals in Melbourne for the 11th consecutive year.
The Swiss showed his class against a tought opponent, setting up a quarterfinal meeting with Andy Murray, who needed four sets to dispatch lucky loser Stephane Robert of France 6-1, 6-2, 6-7 (6-8), 6-2 in two hours and 42 minutes.
Despite beating Federer at Roland Garros last year, Tsonga couldn't get close to the 17-time grand slam champion who produced his most impressive showing of the championship and provided evidence he can be a threat to the likes of Nadal, Murray and Djokovic.
"It's been a different type of tournament," said Federer. "It's been fun, it's been a good ride. I thought I played really well tonight. You've got to bring your best game (against Tsonga), because he dictates play a lot. I think I did a good job dictating play."
Nadal made through to the quarterfinal overcoming 16th seed Kei Nishikori 7-6 (7-3), 7-5, 7-6 (7-3). He next faces Grigor Dimitrov of Bulgaria.
Nishikori was in fine form but the powerful Spaniard was too much for the Japanese, eventually taking a long and tough three-setter which lasted over three hours.
Dimitrov, the 22-year-old 22nd seed, showed character beyond his years to overcome the unseeded Spaniard Bautista-Agut 6-3, 3-6 ,6-2, 6-4 in two hours and 24 minutes.
Dimitrov's serve was a major asset, slamming 11 aces with the fastest at 219kph.