'I practised with Federer, Nadal and Djokovic - it's clear who the greatest ever is'
Even as the Big Three era reaches an end, the rivalry between Roger Federer, Rafael Nadal and Novak Djokovic continues to stir a debate. By the numbers, Djokovic is clearly the greatest of all time. But plenty of people in the tennis world bring other things into the argument - influence, reputation, popularity.