Defending champion Novak Djokovic was dragged into a rerun of last year's epic Australian Open final as he edged a gripping five-hour battle with Stanislas Wawrinka in the early hours of Monday.
As women's number two Maria Sharapova enjoyed the smoothest progress in tournament history, it was a very different story in the men's competition as Djokovic was taken to five sets by the inspired Swiss.
Djokovic ripped off his shirt in celebration after finally clinching the 5hr 2min thriller at 1:41 am, evoking memories of last year's 5hr 53min final with Rafael Nadal, the longest Grand Slam title match in history.
But it is questionable whether the Serbian world number one, who now faces Tomas Berdych, will be in sufficient shape to seal the first hat-trick of Australian Open titles of the professional era.
"It's really hard to find the words to describe the feeling that we had tonight, especially in the fifth set," Djokovic said. "He (Wawrinka) deserves equally to be the winner of this match.
"It brings back the memory definitely of 12 months ago with Rafa."
Wawrinka, the world number 17, resembled his close friend Roger Federer as he smoothly ripped one-handed backhands on the way to breaking the stunned top seed three times in the first set.
Djokovic fought back to take the next two sets but Wawrinka clinched a fourth set tie-breaker to take it into a post-midnight decider in front of an excited crowd at Rod Laver Arena.
Both players exchanged early breaks in the nerve-jangling fifth set but the score blew out to 11-10 and both players were limping and wincing before Djokovic finally clinched it 1-6, 7-5, 6-4, 6-7 (5/7), 12-10.
Earlier Sharapova had no such problems as she clocked up her fifth 6-0 set score of the first week and blitzed Kirsten Flipkens 6-1, 6-0 to reach the quarters for the loss of just five games, smashing the tournament record.
Sharapova, the statuesque Russian who clinched the title in 2008, won her first two matches 6-0, 6-0, a double not achieved at a Grand Slam since 1985, and then floored Venus Williams 6-1, 6-3 in the third round.
She beats the event record of eight games lost en route to the last eight, held by Monica Seles and Steffi Graf, and comes close to Mary Pierce's all-Grand Slam mark of four in reaching the 1994 French Open quarters.
The intensely focused world number two has not given her opponents an inch, in a relentless performance which has given backers of Serena Williams, the tournament favourite, second thoughts.
But the four-time Grand Slam winner said her mind never strayed beyond her next opponent, in this case fellow Russian Ekaterina Makerova, her victim in the quarter-finals on the way to last year's final.
"It's not about waiting to see where you are in the semis or finals, it's about who's ahead of you," said Sharapova, a veteran of 38 Grand Slam campaigns at the age of just 25.
However, on Tuesday Sharapova will meet a challenger gunning for revenge in the form of Makarova, who is still smarting from last year's comprehensive 6-2, 6-3 defeat.
As China's Li Na dispatched Germany's Julia Goerges, Poland's world number four Agnieszka Radwanska dominated former world number one Ana Ivanovic as she chalked up her 13th win of the nascent season.
Radwanska's opponent on Tuesday will be Li, the world number six and 2011 French Open champion, who was also impressive in her 7-6 (8/6), 6-1 victory over Goerges as she reached her third Melbourne quarter-final.
"If I had lost the first set it could have been another story," admitted Li. "I just kept going point by point, not thinking too much."
In the men's draw, world number five Ferrer was faultless as he dispatched Japanese number one Kei Nishikori, the 16th seed, 6-2, 6-1, 6-4 to set up an all-Spanish last-eight clash with Nicolas Almagro.
"Today I played one of the best matches of my career at the Australian Open. I'm very happy with my game," Ferrer said. "It was in three sets, but it was very difficult to beat Nishikori."
Czech fifth seed Berdych beat South Africa's Kevin Anderson to put himself into the quarter-final with Djokovic.
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