Mischa Zverev is unsure whether Novak Djokovic can return to the number on in the rankings because it will depend on several things.
He is currently dominating the indoor circuit with some superb tennis. Djokovic appears to be in good shape, and Zverev anticipates him playing for at least 3–4 years. However, his ability to reclaim the top spot would rely on a number of factors.
"The way Novak looks, he can play another three or four years. Age is only a number if you do everything right on and off the court like Novak. But I don't know if he will be world No. 1 again. The big issue will be: Will he play the Australian Open?"
Djokovic himself is very motivated after a lacklustre year this year. Most of it was not due to his play but rather other circumstances which fuels his motivation: "My approach is to win tournaments wherever I am and I’m glad that I have a team of people around me that makes sure that I am in the best shape in order to be a contender to win titles."