“He is a searcher,” said Marian Vajda, his longtime coach and confidant. “It seems that the things are perfect, but suddenly he wants to change in some way.”

Through the years, Djokovic has switched to a gluten-free and dairy-free diet, practiced meditation and visualization and tinkered repeatedly — and not always successfully — with his service motion. He has used a personal hyperbaric chamber during tournaments. Most recently, he split with an analytics consultant in part because Goran Ivanisevic, one of Djokovic’s coaches, believed they needed get to back to “more basics” and not rely on “all these numbers.”

But Djokovic is committed to experimentation.

“There are so many athletes, so many tennis players, who play so well in practice, and then it comes to the match, and it’s a different story,” he said. “You might have a good match or two or a good month or two, but how can you consistently be there? That tonic or formula of success is like a holy grail for any athlete. How can I really optimize everything and be in a balanced state of mind, body and soul every season for the rest of my career and really be able to peak when I need to?

“I think the No. 1 requirement is constant desire and open-mindedness to master and improve and evolve yourself in every aspect. I know Roger has been talking about it, and it’s something I feel most top athletes of all sports agree on. Stagnation is regression.”

For Vajda and for Djokovic, the restlessness helps explain the pull of the philosophical. Djokovic is trying to channel some of his innate fire and temper it, too.