"I am not obviously as comfortable on the net as I am on the baseline, but I've been working on it," Djokovic told reporters. "It's part of my game that I still need to improve. I'm aware of that.
"It makes me happy that I have room for improvement, and I keep on spending hours and hours on the court and working on variety in my game.
"And serve, especially that part of my game. I want to try and get as many free points on the serve as possible."
Djokovic was beaten in the final at the US Open last year by Andy Murray.