Roundup: Cibulkova into Australian Open quarters

The diminutive Slovakian Dominika Cibulkova moved one step closer to her maiden Grand Slam title with a tight fourth round win over two-time champion Victoria Azarenka at the Australian Open on Monday.

In the standout match of the women's draw so far, last year's finalist forbid the 2012 and 2013 champion from dominating the baseline and instead, through sheer force of powerful forehands, prevailed 6-2, 3-6, 6-3.

Cibulkova will play world No.1 Serena Williams who won in three sets over Spain's Garbine Muguruza, while defending men's champion Stan Wawrinka defeated another Spaniard in Guillermo Garcia-Lopez to advance to his third straight Grand Slam quarterfinal.

Asia's No.1 male Kei Nishikori of Japan won the battle of the counter-punchers to move past David Ferrer of Spain 6-3, 6-3, 6-3.

At 3-3 in the third set, Cibulkova and Azarenka became aware their deadlock, characterized by long rallies and longer service games, would only end with a moment of brilliance.

Cibulkova produced it, after noticing Azarenka caught meters behind the baseline and playing a deft, if risky, drop shot to bring up break point.

"I knew I had to go for it at more than one hundred per cent," said the Slovak.

Azarenka was unable to reply with her own magic moment as the world No.10 dictated play from the serve and pushed the usually-aggressive Belarusian uncomfortably back into her shell.

Cibulkova often wrong-footed her opponent, striking explosive 21 winners in just eight games, and pressured the retreating Azarenka into a reactive style.

The commanding Azarenka who had raced through the first week went missing as Cibulkova gradually moved the sheepish former world No.1 further back and wide before unleashing yet more flashy forehands.

Azarenka turned the tables in the second, but as the third set reached its crescendo, Azarenka again retreated and waited.

On a day where Cibulkova was seeing the ball like a watermelon and unapologetic in her attack, there would be only one result.

"I'm not like a typical small player...I'm going for it and that's what my tennis is about."

Five-time champion Serena Williams has avoided being bundled out in the fourth round by 24th seed Muguruza.

Williams, who last won the Australian Open in 2010, narrowly avoided defeat to triumph 2-6, 6-3, 6-2 after the Venezuelan-born Spaniard took the ascendancy early.

Williams won just one of 12 second serve points in the first set as the world No.24's anticipation ripped control from the American.

During a 13-minute Williams service game in the third set, Muguruza had not one, but six chances to take the lead and move closer to a quarter-final against Cibulkova.

She scuppered every opportunity.

Having survived her greatest trial of this tournament, Williams pushed back and broke serve against the run of play.

When asked what she thought about coming up against the in-form Cibulkova, a relieved Williams retorted "I don't care. I'm into the quarter-finals."

World No.5 Nishikori will meet last year's champion, Wawrinka, in the quarter finals after the Japanese player reluctantly went for his shots and maintained serve best.

With both players used to playing passively against stronger opponents, Nishikori took his chance to take the match by the scruff of the neck.

It did not always work for him - 44 unforced errors to 43 winners showed that - but by attacking Ferrer's weak second serve, he managed six breaks and comfortably equaled his best result at Melbourne Park. ' Nishikori's next opponent, Wawrinka, backed himself into a corner but fought his way out to continue his unbeaten streak in 2015.

Having won the first two sets, Wawrinka played passively in the next two and only his saving of five set points in the fourth-set tiebreak prevented Guillermo Garcia-Lopez pushing the match to the full distance.

"I tried to focus on each one but it wasn't easy," said the 2014 champion of defending the set points.

Wawrinka eventually prevailed 7-6 (7-2), 6-4, 4-6, 7-6 (10-8) but lamented his mistake to invite Garcia-Lopez back into the match.

"I was a little too defensive in the third and fourth sets," said Wawrinka.

In the battle of the American Madisons, world No.35 Madison Keys held off compatriot Madison Brengle to win 6-2, 6-4.

The 19-year-old's first Grand Slam quarter-final will be against a seasoned professional: either Venus Williams or Agnieszka Radwanska. Endi