Australian Open PHOTOS: Kvitova upset by Keys; Djokovic, Azarenka safely through

Images from the Australian Open matches played on Saturday

American teenager Madison Keys toppled fourth seed Petra Kvitova 6-4, 7-5 in an impressive display of clean hitting to reach the fourth round of the Australian Open on Saturday.

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The 19-year-old captured the decisive break at 5-5 in the second set and served out the match nervelessly under the lights of Rod Laver Arena, stunning the two-time Wimbledon champion.

Keys' win made it four American women in the last 16 at Melbourne Park, the most since five made it to the fourth round of the 2003 Australian Open.

She will play compatriot Madison Brengle for a place in the quarter-finals.

"I think my hands are still shaking," said Keys, who is coached by former number one Lindsay Davenport.

"I'm excited to play Maddie in the next round."

Azarenka grunts her way into fourth round

Two-time champion Victoria Azarenka won a battle of former girls' champions at the Australian Open by easing past Czech Barbora Zahlavova Strycova 6-4, 6-4 on Saturday to advance to the fourth round at Melbourne Park.

A double break down in the second set, 25th seed Zahlavova Strycova scrapped hard to get back on level terms at 4-4, but she promptly lost focus to hand Azarenka another break the following game.

Strycova gave up match point by botching an easy volley into the tramlines and surrendered by clubbing a forehand long, allowing a scratchy Azarenka to win in one hour and 46 minutes without playing near her best tennis.

Azarenka will play last year's finalist Dominika Cibulkova for a place in the quarter-finals.

Djokovic safely through

Top seed Novak Djokovic overcame a nervous start and feisty Fernando Verdasco to safely negotiate his way into the fourth round.

With the surprise loss of Roger Federer still hanging over the men's draw, Djokovic was well aware the danger the 31-year-old Verdasco, a former top-10 player posed.

The Spaniard had taken Rafael Nadal deep into the night in a five-hour, five set marathon during the 2009 semi-finals in Melbourne and only trailed the Serb 6-4 in their career head-to-head record.

Verdasco harassed Djokovic at the start but once the world number one sealed the first set tiebreak after an hour of the tense baseline battle he ran away with the match in the next two to win 7-6(8), 6-3, 6-4 and set up a fourth round clash with Luxembourg's Gilles Muller.

Djokovic's match, which was temporarily halted before the third set as Verdasco took a timeout, did have another distraction with a marriage proposal in the stands that the world number one applauded when the woman accepted.

"I'm sure he was very happy when she said yes," a smiling Djokovic said. "It's nice to see this moment."

Wawrinka safely through to fourth round

Men's champion Stanislas Wawrinka avoided a repeat of the stunning upset of compatriot Roger Federer on Friday, with a 6-4, 6-2, 6-4 win over Finland's Jarkko Nieminen, while eighth seed Milos Raonic cruised past Germany's Benjamin Becker 6-4, 6-3, 6-3.

Wawrinka actually had major troubles with his first serve, with it hovering at less than 50 percent for much of the match, but still managed to win his service games and dominate the majority of the short rallies.

"I'm really happy with my game so far, I was aggressive, took control of the match and I think my game is there. I'm happy to get through again," Wawrinka said in a courtside interview.

""I've been here 10 days before the tournament and this is a new challenge for the next two weeks and that is what I'm focussed on."
"I'm not the focus on the tournament because there's Novak, Rafa coming back from injury, Roger also just lost, there's Kyrgios, Tomic still playing," Wawrinka said.

"For me, doesn't matter."