Slovakia’s Dominika Cibulkova has caused the second huge women’s upset at the Australian Open in as many days, downing third seed Maria Sharapova in the fourth round.

The 20th-seeded Cibulkova won 3-6 6-4 6-1 in a match lasting two hours and 12 minutes.

Sharapova’s defeat came less than 24 hours after world No.1 Serena Williams went down to Ana Ivanovic, and further opened up the women’s draw.

After winning the first set, Sharapova quickly went 5-0 down in the second.

She rallied to win four straight games, only for Cibulkova to serve the set out at the third time of trying.

“That was a really, really important game to stay in the match,” said Cibulkova.

“It could have been very different if it was five-all.

“In this game I was going for my shots and I played really well.”

The Slovakian then dominated the decider, setting up a quarter-final against No.11 seed Simona Halep from Romania.

Halep reached the last eight at a grand slam tournament for the first time in 15 attempts with the 6-4 2-6 6-0 victory over former world No.1 Jankovic.

Two-time defending champion Victoria Azarenka from Belarus is now the only previous Australian Open winner still in contention for the 2014 title after downing American Sloane Stephens 6-3 6-2.

“It was a tough match and I was ready to battle as long as I needed to,” said Azarenka after beating Stephens in a repeat of last year’s semi-final at Melbourne Park.

“I knew I had to play my best to beat her.”

Azarenka will play either No.5 Agnieszka Radwanska from Poland or Spain’s Garbine Muguruza in the quarter-finals.

Cibulkova, 24, is now in uncharted territory, having reached the Australian Open quarters for the first time.

“Obviously it feels great and especially I played well and it was a tough match,” she said.

“That was the important thing, that I went on the court and was 100 per cent sure that I could win the match.”

It was the second time that Cibulkova had ousted Sharapova from a grand slam event.

The other occasion was an even bigger upset, when the Slovakian won 6-0 6-2 in the quarter-finals of the 2009 French Open when she was ranked a lowly No.102 in the world.

Sharapova had reached the final at Melbourne Park on three previous occasions, winning the title back in 2008.

Sharapova took a medical timeout at the end of the second set to receive treatment on a hip strain, but declined to use it as an excuse for the loss.

“I haven’t been playing the best tennis of this tournament but I found ways to get through the last two matches,” said the Russian.

“I tried to do that again today, but she played extremely well.”

Sharapova was also troubled by a hip injury last year at Wimbledon, with the Brisbane International earlier this month her first tournament since mid-August.

“I have to look at the positives and see where I have come from in the last four or five months,” she said.

“I would certainly have loved to play a little bit more before playing a grand slam, but this is the chance I was given.”