If Murray wants to keep it simple, winning the World Tour Finals would make him the year-end No.1.There are other, more complicated scenarios in which he can still finish 2016 atop the rankings, though: if he matches or does better than Djokovic; if he finishes runner-up with three round-robin wins and the Serb wins the title with one round-robin win; or if Murray wins three round-robin matches and Djokovic is runner-up with one round-robin win.Djokovic is far from helpless in this, however. If he successfully defends his title with at least two round-robin wins, he will finish as the No.1 for the fifth time in the past six seasons.