Wimbledon 2013: Being as bendy as Uri Geller's spoons has helped Novak Djokovic reach the top of the world Murray, at least, intuits exactly what he is facing from his former nemesis in juniors. "Novak is able to fight until the last point of every match," he argues. He never really has any let-downs during a match, which he used to when he was younger. But it is not merely Djokovic's astonishing battery life that leaves even his opponents agasp. It is his remarkably elastic frame, forged from a dedication to eye-watering stretching exercises, that constantly forces his adversaries to retrieve another ball or play an extra point. "I take pride in that," the world No 1 admitted. I consider it to be the result of all the hard work I put in. How, precisely, has he done it? It appears that his flexibility does not owe everything to his present fitness regime, under the control of coach Marian Vajda, but that it originated far earlier, with the instruction of childhood mentor Jelena Gencic. Djokovic's debt to his former mentor in Belgrade, who died during last month's French Open, has been self-evident here at Wimbledon, for it was she who first imparted to him the virtues of all-round fitness, beyond purely technical teachings. "You know how he is now so flexible - do you know why?" she once asked. It is because I didn't want to work too hard with him. Pointing to a racket, she explained: "This is the heaviest thing he had to handle. We only worked on his legs, quickness on the court, not in the weight room. We stretched and did special movements for tennis, to be agile and fast with the legs. Now he is excellent. That would be an understatement. Djokovic is poised to engage in another fearsome baseline duel with Murray, lunging into the corners to retrieve even the most powerful smashes. His genetic make-up plays some role - his father Srdjan, after all, was a competitive skier. However, Gencic supplied the crucial impetus, appreciating how great a role endurance would play in the modern game and urging her pupil to take care of his muscles. Djokovic reflected: "She would teach me that if I stayed flexible, I would not only be able to move well around the court and recover well, I would have a long career." Her prophecy has been borne out - since he first started competing in the majors in 2005, he has not missed a single slam. So highly does Djokovic prize his Transformer-like physique that he claims to keep a picture back at his apartment in Monte Carlo, of him striking a backhand return with his left leg high above his head. It was no optical illusion. So prodigiously bendy has his body become that, when he reports for morning training, it is reputed that he is able to drape his leg over the shoulder of his physiotherapist, Miljan Amanovic, without so much as warming up. Gebhard Phil-Gritsch, Djokovic's fitness trainer, is reticent whenever he is pressed on how Djokovic can pull off this kind of move before breakfast, ascribing it purely to hard work. But there are other facets, not least the 26-year-old's habit of carrying out stretches when he is not even on the practice court. "When he is waiting for a car, when he is doing anything around the grounds, it seems like he is always stretching something," one-time Wimbledon finalist Jim Courier observed to The New York Times. He's doing his arms or his trainer has his hands behind his back, and he is pulling. There have been dietary changes, too, not least a decision to switch to a gluten-free diet ahead of his maiden US Open title in 2011. Djokovic insisted that the change had enhanced his mobility, and yet his physical transformation has extended far beyond that. "It is the rhythm that we have come to expect over the years that has brought us so much success," he said. So we don't want to change that because we know that it makes me feel good. And when Djokovic feels good, as Murray all too keenly knows as the veteran of two slam final defeats to him, there tends only to be one outcome.