Jannik Sinner says he still has areas where he can improve next year after winning the ATP Finals for the first time Sunday to cap a near-perfect season for the world number one. The 23-year-old Sinner beat Taylor Fritz 6-4, 6-4 at the season-ending event in Turin, his eighth title of a remarkable season which began with a first Grand Slam triumph at the Australian Open. He followed that up with a second major victory at the US Open in September after becoming embroiled in a doping controversy having twice tested positive for traces of the steroid clostebol six months prior.