Melbourne - Novak Djokovic refused to reveal details of his recovery programme on Tuesday but stressed it did not break any rules after he bounced back from a marathon match to reach the Australian Open semi-finals.
The world No 1 and defending champion steadfastly blocked questions about his recovery after he appeared unaffected in his quarter-final despite playing for five hours against Stanislas Wawrinka two days earlier.
Djokovic, 25, playing freely and doing his trademark splits and slides across the court, beat Czech fifth seed Tomas Berdych 6-1, 4-6, 6-1, 6-4 in 2hr 31min to set up a semi-final with David Ferrer.
His performance was in stark contrast to Gilles Simon, whose third round evening match also took five hours but left him badly incapacitated when he took on Andy Murray in the next round.
"I felt good enough to go another five hours, but I definitely wasn't thinking about it," Djokovic said on Tuesday. "I tried to get the work done as fast and efficient as possible."
Djokovic said he went to bed at 05:00 on Monday after his five-setter with Wawrinka and woke up at 14:30. Beyond saying he took an ice bath, walked in the park and watched TV, he did not give details of his recovery.
Berdych said he was not surprised by Djokovic's condition. Last year the Serb, who was once known for his physical frailty, won a six-hour final against Rafael Nadal, after a five-hour semi-final against Andy Murray.
"If Stan would be the one who won, then we would probably see it would affect him. But definitely not for Novak. I mean, he's probably the fittest guy on tour right now," said the Czech.
"I've seen him play really much better. But it's not that I'm saying something against him. I mean, all the credit that he was able to (recover) from that. It just shows how fit he is."
Djokovic is also coy about details of the training regime which has taken him to the top of the sport over the last two years. He said his team had routines in place to help him recover quickly from big matches.
"People who don't know tennis, who have never been in those kinds of situations would not truly understand what the player has to go through, not just when you prepare for a Grand Slam, but also during a Grand Slam," he said.
"After five hours of match, you need to really put a lot of time into recovery, different kinds of recoveries. As I said, I understand that many people have many different views and opinions, and I respect that.
"But I'm doing everything that is legal, that is correct, that is natural that I can, possibly can in my power, and it's working well."
In 2009, when he was also the defending champion, Djokovic pulled out of the Australian Open during his the fourth set of his quarter-final against Andy Roddick, citing exhaustion in the intense summer heat.
"Everybody makes mistakes. I was aware of the fact that I need to improve because I wasn't feeling well, especially in the heat. I had lots of health issues," he said.
"Maybe that's one of the reasons why I'm being so cautious and so committed when recovery is in matter because I've had those experiences, bad experiences, before in my career and I know what it feels like.
"I don't want to go through it again. I am aware of the importance of an everyday practice and recovery basis. So as long as it's like that I think I'll be all right."
Djokovic is not the only player to recover impressively in Melbourne. In 2009, Nadal was extended over five hours in the semi-finals by Fernando Verdasco, and he then beat Roger Federer in the five-set title match.