With Novak Djokovic having secured his latest win at Wimbledon, there is no shadow of a doubt that he is not the greatest tennis player of all time. He has now won 20 Grand Slams. Given that he is 34, and that he has been playing pro tennis since 2003, that is no mean feat at all. He has also been ranked No. 1 by the Association of Tennis Professionals for a staggering 329 weeks.