* Djokovic survives scare
* Sharapova sets Australian Open record
* Radwanska registers 13th straight win
By Nick Mulvenney
MELBOURNE, Jan 20 (Reuters) - Novak Djokovic survived an almighty scare from an inspired Stan Wawrinka in a five-hour, five-set thriller at the Australian Open on Sunday, reaching a 15th consecutive grand slam quarter-final but only after digging himself out of a huge hole.
For the first 50 minutes of the contest, Wawrinka played as if possessed by his compatriot Roger Federer and confounded the world number one with brilliant backhands and ferocious forehands to notch up five straight breaks of serve.
Even when Djokovic had weathered the worst of the storm and clawed his way back from 6-1 4-1 down to win the second and third sets, the world number 17 made the Serbian earn every point and forced a decider after a dramatic tiebreak.
The Swiss blew four precious break points in the ninth game of the fifth set and Djokovic converted his third match point with a brilliant backhand winner to seal a 1-6 7-5 6-4 6-7 12-10 win.
In a conscious echo of his win over Rafa Nadal in last year's nearly six-hour final on Rod Laver Arena, Djokovic ripped off his shirt and roared in delight at a victory which kept alive his hopes of a third successive title at Melbourne Park.
"We are only halfway through the tournament but it felt like a final to me," said Djokovic, who will meet fifth seed Tomas Berdych in the next round.
"He deserved equally to be a winner of this match. Tonight he showed his qualities. He was the aggressor on the court and I was just hanging in there trying to fight.
"I always believed I could win the match and I am absolutely thrilled to be in the next round. It certainly brings back memories of last year with Rafa."
Wawrinka, who left the court with tears in his eyes, was distraught after coming up short despite playing the match of his life.
"I think it's the best match I've ever played," he said. "At the end I was really close and I was really sad to lose, it was a great disappointment for sure."
In the women's draw it was business as usual as Maria Sharapova progressed with brutal efficiency to reach the last eight having lost just five games all week - an Australian Open record.
Agnieszka Radwanska continued her perfect start to the year with her 13th successive victory to set up a quarter-final with Li Na, while David Ferrer eased further into the gap in the draw left by his injured compatriot Nadal.
Injury-hampered fifth seed Angelique Kerber crashed out, however, and she was joined at the exit by men's eighth seed Janko Tipsarevic, who retired from his tie with a foot problem after spending more than 11 hours on court in his four matches.
Sharapova has achieved her four wins in just 249, earning more than $1,000 a minute given the $250,000 purse for quarter-finalists.
The second seed was held up briefly when her serve deserted her in the first set but she still hammered Belgian Kirsten Flipkens 6-0 6-1 to set up a repeat of last year's last eight clash with compatriot Ekaterina Makarova, who upset Kerber 7-5 6-4.
"I didn't start the match really great (but) then I started really getting under the ball and being aggressive and just had a little bit more energy," Sharapova said.
Ferrer has reached the quarter-finals for the third straight year with much less hoopla than Sharapova but with almost as much efficiency.
On Sunday, he prowled the baseline of the Rod Laver Arena to great effect and ended the challenge of error-prone Japanese Kei Nishikori 6-2 6-1 6-4.
"It's very important to get to the second week not feeling too tired and in good physical condition," said Ferrer, who will face Nicolas Almagro in an all-Spanish quarter-final.
Fifth seed Berdych had said playing big-serving South African Kevin Anderson would be like facing himself but the contest only really came to life in an epic third-set tiebreak, which the Czech won 15-13 to claim a 6-3 6-2 7-6 win.
Radwanska made four unforced errors to 34 for Ana Ivanovic in their fourth round tie and sealed a 6-2 6-4 rout of the former world number one with her seventh ace.
"She's a player, it's no secret, who doesn't make too many winners, but she has good hands," said Serbian Ivanovic. "She can really get the opponents to feel a little awkward and make you go for too much."
Li converted all five of the break points she earned in her 7-6 6-1 win over Julia Goerges to reach the last eight of a grand slam for the first time since she won the French Open.
"I'm really looking forward to the quarter-final," said the Chinese, a losing finallist here two years ago. "It's been 1-1/2 years. I kept losing in the fourth round so for me it was a very important match today."
Almagro was the beneficiary of Tipsarevic's retirement.
"That's not the way you want to win," said the 10th seed, who was leading 6-2 5-1 when the Serbian decided he could not continue. (Editing by John Mehaffey)