Becoming injury free is not just luck, it is hard work, determination and taking care of the body and Roger Federer excels in that department.
That is true, if you take care of your body, you have better chances of be injury free. But sometiems some players simply have bad luck and are prone to injuries, and that is part of the sport.Many good talents are ruined because they didnt have luck with injuries,that is how it goes.
About Djokovic,i think that vegan diet didnt help him at all.Then he also had some type of guru with him that i think also messed up with him a bit.Alternative lifestyle is not good for pro athletes i think,and if he didnt go that way he would dominate even more.