Is Djokovic's level of endurance attainable without doping?
Outside of actual incriminating doping evidence, that's the key question, and no one has addressed this systematically. I have no clue as to the answer - I assume this is the domain of physiotherapists and such.
As long as we can't even answer this question in a scientific way, it seems silly to toss around doping allegations. I wouldn't be too surprised if tennis was as dirty as 90's/2000's era baseball, but assuming the worst is just as dumb as assuming the best.