Novak Djokovic has sealed his place in the last eight of the Australian Open after beating Gilles Simon in five sets. Djokovic, 28, was pushed all the way by the Frenchman, clinching a 6-3, 6-7, (1-7), 6-4, 4-6, 6-3 in a contest that lasted over four and a half hours.

The world number 1 will take on Kei Nishikori in the next round.

"In terms of a level that I've played, it's the match to forget for me," Djokovic, who made 100 unforced errors despite his victory, said. "But you have days like this, fortunately you manage to fight your way through.

"It's not a very pleasant feeling when you're not playing well. But certainly it's a good feeling when you win not playing well."

Nishikori meanwhile sealed his place in the final eight with a 6-4, 6-2, 6-4 win over Jo-Wilfried Tsonga.

Roger Federer has also booked his place in the last eight after easing past Belgian David Goffin in straight sets, his 12th quarter-final appearance in Melbourne.

Defending champion Serena Williams will meet Maria Sharapova in the quarter-finals after hammering Margarita Gasparyan 6-2, 6-1 in 55 minutes. 2008 champion Sharapova sealed her place with a 7-5, 7-5 win over Belinda Bencic.