Alexander Zverev makes his #NittoATPFinals debut a memorable one by outlasting Cilic 6-4, 3-6, 6-4 in Group Boris Becker. Send him a 🇩🇪 for great fighting spirit today! (📸: @alexzverev123) #usopen #alexanderzverev #saschazverev #atp #tennis #protennis #instatennis #instasports