Novak Djokovic says the reason he was finally able to sustain his top level and take over the No. 1 ranking was primarily because he was able to improve his psychological approach to the game.

“I think it was mental in the end,” he told reporters in Miami. “Bottom line is this is a mental game. Everybody can work very hard during the day on their physical condition and achieve a certain level of the game. But in the big matches and at big tournaments, in the close moments, the player who is calmer and who is more mentally composed and who has more experience usually wins the match.

"So I have been No. 3 of the world since I was 19, 20 years old, in next three or four years, and during that period I was very, successful, but still wasn’t managing to make that extra step and start winning majors and challenging [Roger] Federer and [Rafael] Nadal for the top spot of the world. It was a process of learning, understanding who I am, what I need to do on and off of the court, maturing.”