Novak Djokovic has taken aim at tennis's double standards, frustrated by being "kept in the dark" during Jannik Sinner's doping case. Key Events United Cup: Jasmine Paolini crushes Belina Bencic 3 hours ago United Cup: Germany gets its clean sweep 3 hours ago 'It's not a good image for our sport': Djokovic 5 hours ago Show all key events Sunday's …