Serena Williams worries of hypocrisy after Jannik Sinner's three-month doping ban / Jannik Sinner considered quitting tennis during fallout from doping case / Sinner considered taking a break from tennis before he accepted 3-month ban in doping case / Case closed, but doping still on radar as Sinner nears end of ban / World No.1 Sinner reveals he nearly quit tennis amid doping turmoil / Serena Williams on Sinner doping case: 'I'd have been banned for 20 years' / Serena Williams on Jannik Sinner doping case: I'd have been banned for 20 years / Sinner on doping ban: 'You have to choose the lesser evil' / Djokovic says tennis players have a 'lack of trust' in doping agencies after Sinner case / RUSADA reports eight suspected violations of anti-doping rules in March