Tired and weary, Novak Djokovic lamented a match to forget against Gilles Simon but the world number one refused to dwell on the performance as another Australian Open quarter-final looms.

Djokovic was well below his best but still managed to see off the Frenchman 6-3 6-7 (1-7) 6-4 4-6 6-3 in a marathon lasting more than four hours on Sunday.

Five-time Australian Open champion, and last year's winner, Djokovic made 100 unforced errors and won just 113 of 244 points from the baseline in an uncharacteristically wasteful display on Rod Laver Arena.

While the performance was less than impressive, Djokovic paid tribute to Simon and quickly looked ahead to a 27th consecutive quarter-final appearance at a grand slam.

"I was obviously pleased to win the match. The last point counts. But in terms of the performance itself, I haven't done well at all," Djokovic said post-match.

"But, you can expect unforced errors when you're playing Gilles Simon who is one of the best counter-punchers in the tour at the moment and he's been around for many years. He likes to play long matches. He likes to play long rallies.

"But I honestly didn't expect to make this many unforced errors. In terms of a level that I've played, it's the match to forget for me.

"Again, I won it, so it's pretty good. When you're playing that bad and still manage to win - hopefully it's going to be better next one."

Next up for Djokovic is Japanese seventh seed Kei Nishikori, who ousted Jo-Wilfried Tsonga on Sunday.

Asked if the performance concerned him moving forward, a smiling Djokovic said: "It gives me great joy to know that I can't get worse than that, than what I played today.

"It doesn't concern me for the next one."

Djokovic added: "I've been in these situations before. The good thing about grand slams is that you have a day off in between, which gives you enough time.

"I've had worse situations where I had much less time to recover after long matches. So I'm sure I'll be fine."