Watch as Juventus and Portugal striker Cristiano Ronaldo gets involved in ball kid duties at the Nitto ATP Finals. About CR7, Djokovic said: 'it's great to have big football star, sports star like him, courtside watching tennis. He used to come and watch a lot in Madrid. Rafa, of course, Roger, myself. He's a fan of tennis. It's really, really nice', admitted Nole.