He had just lost the French Open semi-final to Rafael Nadal. Nobody enjoys losing but few players do crushed quite like Djokovic.

Perhaps this is not surprising. Most of his peers see the sport in terms of forehands and backhands, serves and returns. If they have a bad day, they say that their ball toss was off or their volleys were shonky.

Djokovic has a different view. For him, a tennis match is a mental battle, in which the racquets are mere furniture. If you lose, you have failed to meet the challenge inside your head. Rather than rushing down to the practice court, he is more likely to respond with a deep bout of soul-searching.

"In the end, it's a mental game," Djokovic said this week. "When you are playing at that level, with one of your biggest rivals, physically and game-wise everybody is so developed and so committed and disciplined. The bottom line is that mental determination and desire is going to determine who is going to win. There's some factors you can influence, and some you can't. It helps if you are fresh in your mind."

Djokovic rarely makes excuses. Once an impish, even brattish upstart of the locker room, he has taken Roger Federer's lead and matured into a dignified statesman. Yet there is one obvious reason why his focus might have faltered in Paris a fortnight ago.

For the second year running, he had lost someone dear to him during the springtime sequence on European clay. In 2012, he had been devastated by the death of his grandfather Vladimir, which happened in Belgrade while he was more than 1000 kilometres away at the Monte Carlo Masters. "I didn't have any emotional energy left," Djokovic admitted after an understandably distracted performance in the final. "I just wasn't there."

This year, Djokovic's childhood coach Jelena Gencic passed away during the middle weekend of Roland Garros. Actually, the word "coach" feels like an understatement: he described her as his "tennis mother", and promised her last month he would bring back the French Open trophy.

Without Gencic as his guru, it is difficult to imagine he would ever have become a professional player, let alone have accumulated six grand-slam titles. "I still didn't go to Belgrade," Djokovic said. "It happened very recently, so I didn't go and have the tribute to Jelena. I didn't go to visit the cemetery, but I will, the first available moment after Wimbledon.

"It's life. I cannot look at it on the negative side. Yes, I did have some difficulties handling this kind of unexpected moments. But I had to handle it, and I think I handled it really well, because it was in the middle of Roland Garros, and I managed to get to the semi-final and play a thrilling match against Rafa.

"I cannot say that I overcame that kind of grief that I felt inside. It's still there because it's still fresh. But I also try to focus on the nice memories that I had with her. My first coach and mentor, a friend and a lady that really contributed a lot to what I am now."

Gencic helped create the seamless, flowing style that is Djokovic's trademark. More than anybody on the men's tour, his game is about the calibration of risk. Nadal overpowers opponents with his discus-throwing forehand; Roger Federer dances to the net and fizzes volleys like firecrackers; Andy Murray is always thinking at least two shots ahead. But Djokovic has mastered the art of threatening the lines without stepping over them.

He stands more than 3000 rankings points clear of the field as a result of simple geometry: he hits the ball deeper and wider than his rivals. That ability stems not only from the purest technique but the ability to banish fear and achieve a sort of meditative state. You could call him the Zen master of tennis.

"You are what your thoughts are, and that reflects on the court," Djokovic said. The philosophical moment recalled a saying of Mahatma Gandhi: "A man is but a product of his thoughts. What he thinks, he becomes."

Djokovic continued: "If you are on the court, thinking about yourself and trying to focus your attention on positive thoughts, it radiates through you and your opponent feels that. So there's this mental battle going on. Last year, at Wimbledon and the Olympics in the important matches, I don't feel that I had the mental freshness that could decide a match. Maybe losing to Nadal in the final of the French Open affected me. But when I won the next tournament in Toronto, I changed the environment and I felt that I'm back where I want to be. I learned from that experience."

The pain of Djokovic's twin defeats to Nadal on Court Philippe Chatrier has been especially acute. The French Open is the title he wants most, the only one of the major four he has yet to land. Had he done so this year, rather than squandering a 4-3 lead in the deciding set of the semi-final, who knows where the resulting sense of invincibility would have taken him.

"If Novak had got over the line that day, he would have had a great chance of doing the calendar grand slam," says former world No.1 Jim Courier. "These guys are capable of winning on any surface but for Novak, Rafa in Paris is the biggest hurdle."

Tennis, above all sports, is about dealing with tension. Your body has to stay loose at the critical moments to generate the smooth, fluid power required of a successful stroke.

If a man is a product of his thoughts, then Djokovic's greatest talent is his ability to visualise the winner he is about to hit, rather than the howler he might commit. When he takes the applause of the Centre Court crowd next week, part of him will imagine Wimbledon's silver-gilt cup above his head.

Telegraph, London