"I guess I'm going to skip the morning hours and stay in the bed," Djokovic said after outlasting Swiss underdog Stanislas Wawrinka in a five-set, five-hour two-minute thriller that finished at almost two o'clock on Monday morning.

But having survived a similarly sapping four-hour 50-minute semi-final against Andy Murray last year and then overcoming Rafael Nadal in a near-six-hour championship decider two days later, the Serbian ironman believes he can do it again.

Djokovic takes on Czech fifth-seed Tomas Berdych tonight for a place in the semi-finals and is backing his supreme fitness to see him through.

"There is no doubt I'm not very fresh," Djokovic said. "It's normal to expect after five hours of play.

"But still I've been in those situations before. I remember most recently, 12 months ago when I won against Murray in the semis after five hours and then played against Rafa for almost six hours.

"I know I can recover. I know I have it in me."

Djokovic is contesting his 15th consecutive grand slam quarter-final, a streak that surpasses Ivan Lendl's 14 straight and leaves the Serb trailing only Roger Federer (34) and Jimmy Connors (27) for successive last-eight appearances at the majors.

And with a dominant 11-1 win-loss record over Berdych, the world No 1 is a warm favourite to progress to his ninth grand slam semi-final.

Berdych, though, insists he is a different beast to the one that succumbed to Djokovic in the 2011 quarter-finals in Melbourne.

The 27-year-old enjoyed one of his finest seasons in 2012, gaining enormous belief from his US Open quarter-final trumping of Federer and the Czech Republic's historic Davis Cup triumph in November.

"The last year was a pretty, I would say, big year for me," Berdych said.

"There were many new experiences that I learned.

"I hope that I'm going to be able to profit from that," he said.

"On the other hand, last year I spend much more time on court and of course every single piece of energy I'm going to need for the next match.

"But I just play every single match [here] for three sets. Everything is fine.

"I feel physically well. I hope that actually now the big match is waiting for me."

The winner on Thursday will face the victor of today's all-Spanish quarter-final featuring fourth seed David Ferrer and 10th seed Nicolas Almagro for a place in Sunday night's title match.

AAP