Defending champion and World No 1 Novak Djokovic prevailed after a four-hour-long five-set epic against Frenchman Gilles Simon to enter the quarterfinals of the Australian Open on Sunday. Not many had given the the 14th seeded Simon much of a chance and when Djokovic sped to a 6-3 lead in the first set, business seemed to be proceeding as usual. Simon has a reputation for playing gritty tennis though, and he pulled it back, winning the second set with a tiebreak, with Djokovic starting to make many unforced errors.

The Serbian won the next set and looked set to clinch in the fourth set before yet another dogged comeback from Simon, who prevailed 6-4. In a tense fifth set, Djokovic finally managed to break Simon twice and ultimately win 6-3. The final score read: 6-3 6-7 (1-7) 6-4 4-6 6-3.

Djokovic will meet seventh seed Kei Nishikori of Japan in the quarter-finals, in a highly anticipated clash. Nishikori defeated Jo-Wilfried Tsonga in straight sets in his own fourth-round encounter.

The other big seeds, Roger Federer, Stanislaus Wawrinka and Andy Murray all have crucial fourth-round matches coming up.

Over in the women's singles draw, two favourites – Serena Williams and Maria Sharapova – set up a mouth-watering quarterfinal clash on Sunday after winning their fourth round games. Williams had an easy victory against Margarita Gasparyan, taking the game 6-2 6-1, but Sharapova had a tougher time against Belinda Bencic, squeezing out a well-fought 7-5 7-5. Sharapova's serve was her biggest strength as she fired in 21 aces on her way to victory. She will look to use her serve to good effect against Williams as well.

In men's doubles, the pair of Daniel Nestor and Radek Stepanek booked a quarterfinal clash with Treat Huey and Max Mirnyi, who defeated India's Rohan Bopanna and his partner Florin Mergea. There should not be such problems for Sania Mirzia and Martina Hingis who have had a comprehensive campaign so far. They are favourites against Svetlana Kuznetsova and Roberta Vinci in their third round encounter, scheduled for Monday.