Australian Open: Nadal survives Nishikori scare; Sharapova exits

Maria Sharapova joined Serena Williams in making an early exit from the Australian Open on Monday, but defending champion Victoria Azarenka swept into the quarter-finals with an 18th straight victory at Melbourne Park.

A day after Ana Ivanovic's stunning upset of Williams blew open the top half of the draw, third seed Sharapova was also scratched from the title race with a 3-6, 6-4, 6-1 loss to Slovakian Dominika Cibulkova.

Hindered by a hip niggle, the 2008 champion admitted that the year's first Grand Slam had probably come a little early after she missed the US Open and back end of last season with a shoulder injury.

"I certainly would have loved to play a little bit more before playing a Grand Slam, but this is the chance that I was given," the Russian said.

"It's tough. I will be genuine about it. It's never easy (but) it's moments like this that ultimately shape you and make you who you are, and that's how you bounce back."

Men's top seed Rafael Nadal knows plenty about coming back from injury and he did well to fend off a gallant Kei Nishikori and reach the quarter-finals.

Nadal had come hurtling into the match with a brutal demolition of Gael Monfils, but encountered a far different beast in 16th seeded Japanese, who broke his serve for the first time in the tournament and rattled the Spaniard in a 7-6 (7-3), 7-5, 7-6 (7-3) loss at Rod Laver Arena.

The Spaniard's fellow-members of the "Big Four", Roger Federer and Andy Murray, will also be out to seal their places in the quarter-finals. The final member of the quartet, Novak Djokovic, secured his last eight-berth on Sunday.

As the only surviving top three seed left in the women's draw, Azarenka looks to be running out of serious challengers as she charts her course towards a third successive title.

Her 6-3, 6-2 victory over Sloane Stephens had none of the edge of last year's semi-final, when the Belarusian took a medical timeout after blowing five match points, and she sealed a comfortable win in 91 minutes.

CHIPS AND SALSA

Despite taking a ball at full force in the groin -- "I thought she was going to move and she didn't," said Stephens -- the second seed said she could not have felt more at home on Rod Laver Arena.

"I just love playing here. It feels so cosy. It feels like I'm in my living room, on my couch," she said.

"I can have some chips and salsa -- that's how it feels."

The second seed denied that the departure of Williams and Sharapova left her and last year's losing finalist Li Na as favourites for the title.

"I don't consider anybody as the favourite, I just go out there and play my best," she said.

"We've seen over the last couple of days that somebody can bring their best game on any given day. You have to stay alert."

Defeat for Stephens ended all American interest in the singles before the quarter-final for the second time in four years in Melbourne but the 20-year-old said she would be back.

"You just go out and do your best," she said. "Unfortunately I didn't win today, but there will be others."

Next up for Azarenka is the winner of the final match of the day between fifth seed Agnieszka Radwanska and rising Spanish talent Garbine Muguruza.

Cibulkova's reward for beating Sharapova is a quarter-final against Simona Halep, who crouched down and let out a huge roar after a crunching forehand winner gave her a 6-4, 2-6, 6-0 victory over eighth seed Jelena Jankovic.

The Romanian was named most improved player on the women's tour last year after winning six tournaments and has been in impressive form on her way to her first appearance in the last eight at a Grand Slam.

"There's no pressure on me so I can just enjoy the quarter-finals," she said. "It's my chance, and I have to fight for it."

Image: Maria Sharapova of Russia reacts to a point in her fourth round match against Dominika Cibulkova of Slovakia on Monday

Photograph: Ryan Pierse/Getty Images