Novak Djokovic feels Italian teenager Jannik Sinner leads the pack of 'Next Gen' players with the potential of becoming a future world number one, the Serbian said after all but securing his year-end top ranking with a win in Vienna on Wednesday. Djokovic saved four set points in the opener against Croatia's Borna Coric to win 7-6(11) 6-3 to reach the third round of the Erste