(CNN) -- First Serena Williams, now Maria Sharapova. Another day at the Australian Open, another top female star out of the season's first grand slam.
One day after world No. 1 Williams was dumped out in Melbourne, third seed Sharapova followed suit as she surrendered a one-set lead against Slovakia's Dominika Cibulkova to lose 3-6 6-4 6-1.
It was the second time 20th seed Cibulkova has beaten the Russian at a grand slam and Sharapova, who required treatment on a hip injury between the second and third sets, admitted her performances in Melbourne have not been good enough.
"I haven't been playing the best tennis of this tournament, but I found ways to get through to the last two matches," Sharapova, a winner of this tournament in 2008, told reporters.
"Tried to do that again today, but she played extremely well."
Sharapova, a four-time grand slam winner, refused to blame the injury for her surprise defeat.
"I don't think it's rocket science," added the 26-year-old. "Just when you play a lot of tennis, you're going to get these types of aches and pains and certain movements that you feel it on."
Cibulkova's reward for reaching the last eight at Melbourne Park for the first time in her career is a match against 11th seed Simona Halep, who also eliminated a top 10 player in world No. 8 Jelena Jankovic.
Sharapova's loss means double defending champion Victoria Azarenka is now the red hot favorite to win a third consecutive Australian Open title.
Azarenka's cause will be helped by cooler temperatures, with players finally granted respite from last week's scorching heat.
The world No. 2 is the only former champion left in the women's draw after she confidently dispatched American rising star Sloane Stephens 6-3 6-2.
Although her chief rivals for the title have been eliminated, Azarenka is taking nothing for granted ahead of a meeting with fifth seed Agnieszka Radwanska.
"The players who beat those players deserve all the credit because they've been better, so they are dangerous and they are competitive," said Belarus' Azarenka.
"For me it's important to just, you know, keep focusing on my game and play it one at a time. Quarterfinals of a grand slam is never easy, no matter who you play."
While the women's draw is turning out unexpected results, the men's half is proving altogether more predictable.
World No. 1 Rafael Nadal registered a straight-sets win over Japan's Kei Nishikori which was far more difficult than the scoreline would suggest.
The 13-time grand slam champion had his serve broken four times and he was made to sweat by 16th seed Nishikori before wrapping up a 7-6 (7-3) 7-5 7-6 (7-3) win.
Nadal will continue his bid for a second career win at the season-opening grand slam against Bulgarian No. 22 Gregor Dimitrov.
Three-time finalist Andy Murray didn't have it all his own way during his round of 16 victory over Frenchman Stephane Robert.
The world No. 4 looked unflappable as he raced into a 6-1 6-2 lead, but Robert, ranked 119th, rallied to take a third set tie break.
Eventually Murray's class told and the Scot secured a 6-1 6-2 6-7 (6-8) 6-2 win, with 17-time grand slam winner Roger Federer awaiting in the quarterfinals.
Sixth seed Federer looked in ominous form as he swept aside No. 10 Jo-Wilfried Tsonga 6-3 7-5 6-4, showing glimpses of the talent which brought him four Australian Open titles between 2004 and 2010.