Top-ranked Sinner, 24-time Grand Slam champ Djokovic withdraw from the National Bank Open  CTV NewsSinner, Djokovic withdraw from Montreal  ATP TourCanada Masters director airs grievances with ATP after Jannik Sinner and Novak Djokovic withdraw 1 week before tournament  Yahoo SportsSchedule changes called for after Jannik Sinner and Novak Djokovic withdraw from Canadian Open  BBCTop-ranked tennis stars Jannik Sinner and Novak Djokovic withdraw from Canadian Open  Montreal Gazette