If the Australian Open comes down to survival of the fittest, then hand Novak Djokovic the trophy now.

Djokovic proved his remarkable recuperative powers again at Melbourne Park as be rebounded from a sapping five-set marathon 48 hours earlier to move into the semi-finals.

Djokovic was at his clinical best on Rod Laver Arena on Tuesday night, overcoming Czech fifth seed Tomas Berdych 6-1 4-6 6-1 6-4 to book a semi-final clash with fourth seed David Ferrer.

Berdych described Djokovic post-match as the fittest player on the men’s tour, and few would disagree as the nightclub hours the 25-year-old Serbian has been keeping did little to blunt his effectiveness.

But whatever fitness and recovery secrets Djokovic has - as evidenced by his monster semi-final and final victories last year - he’s not sharing.

"After a five-hour match the other night against Stan (Wawrinka), I was quite convinced I could recover for this one, and my (fitness) team did a great job," Djokovic said.

"I can’t say (what my routine is). I keep it private.

"In grand slam tournaments, you have to be ready for five-hour matches, and if you go through those matches, you have to be ready to recover in just a day and a half’s time.

"It’s worked before and we used that necessary experience to implement it in this particular situation, and it worked again."

Post-match ice baths and a gluten-free diet are parts of Djokovic’s fitness regime, as well as being driven by bad memories of early in his career when his fitness wasn’t up to scratch, and he had to pull out of matches.

"At the start of my career I went through a lot of challenges physically and mentally. I wasn’t feeling well, especially in the heat ... maybe that’s one of the reasons why I’m so cautious and committed to recovery," Djokovic said.

"I’ve had those bad experiences before in my career and I know what it feels like, and I don’t want to go through it again."

Djokovic showed he was on his game early in his quarter-final with a break of serve in the third game - one of three in the opening set - as he swept to a one-set advantage.

Berdych broke in the opening game of the second set and struck back, despite squandering a set point and having to save four break points to close out the set on his serve.

However Djokovic, whose first and second serve were deadly throughout, grabbed early service breaks in the third and fourth sets.

It took until his fourth match point, but Djokovic eventually won in two hours and 31 minutes, and importantly at a far more comfortable hour than his early morning finish against Wawrinka.

He now meets Ferrer after the Spaniard survived a rollercoaster five-setter to beat countryman Nicolas Almagro 4-6 4-6 7-5 7-6 (7-4) 6-2 earlier on Tuesday.

smh.com.au