Sjogren’s Syndrome in 2011.
“The first set wasn’t easy, in the second she just started to play better, in the third I think I went into a trance. I just wanted to win,” she said.
Defending champion Stan Wawrinka ensured his passage by winning a thrilling fourth-set tiebreaker to down Spain’s tenacious Guillermo Garcia-Lopez 7-6 (7/2), 6-4, 4-6, 7-6 (10/8).
He now plays Japanese superstar Kei Nishikori, who was a class above dogged Spanish baseliner David Ferrer, easing through 6-3, 6-3, 6-3.
“He’s a tough, tough player. He improved a lot last year,” Wawrinka said of Nishikori.
Former Australian champion Lindsay Davenport’s protege Madison Keys made her first Grand Slam quarter-final, winning an all-American clash with Madison Brengle 6-2, 6-4.
The unseeded world number 35, just 19, has long been touted as the rising star of American tennis and will next play Venus Williams, the 18th seed.
Venus has been keeping tabs on Keys’ progress for years and noted that “she started watching me when she was in diapers”.
Cibulkova, who lost in the 2014 title decider to Li Na, went into her match as an underdog against Azarenka, who had beaten her seven times in their nine previous meetings.
But she said her self-belief blossomed as she stepped back onto Rod Laver Arena, the scene of her best Grand Slam performance.
“I just walked on the court and all the memories came to my mind and I was just thinking ‘I’m a great player, I can do it, I just have to believe in myself’,” she said.
Despite her disappointment Azarenka was content with what she had achieved so far on the comeback trail, including a defeat of eighth seed Caroline Wozniacki in round two.
“I take it as progress. I think there are a lot of the positive things to take from here,” said Azarenka, who won the title in 2012 and 2013 but struggled with a string of foot injuries and bouts of depression last year.