In his wonderful book Strokes of Genius, the Sports Illustrated writer L Jon Wertheim suggests that “child psychologists often say that every adolescent male needs an adult to help him grow up, and it can’t be a father. In Nadal’s case, this was clearly his uncle, a mystical figure who shaped the kid’s tennis game and his core identity in equal measure.” As you might infer, the relationship between Rafa and Toni has a touch of the Lukes and the Obi-Wans about it. Or perhaps of an old sea dog and his eager young cabin boy. 

I sought Uncle Toni out last Friday, at a wet Wimbledon, and found him playing chess in the player’s lounge. His opponent was another Spanish coach, Jose Clavet, who clearly had the King’s Gambit down pat.

Toni’s forces were in sharp decline as Clavet launched a series of frenzied thrusts down the right.

“I am so bad!” Toni exclaimed. “So bad today!”

Happily, though, he was chuckling rather than chuntering. It is part of his philosophy, he told me later, to accept defeat with good grace. Indeed Toni is the only leading coach who regularly applauds winning shots from the opposition camp’s box.

“I believe you must have respect for everyone and everything,” Toni explained, in his workable but slightly halting English. “Not only your opponent, but the court, the racket, the person who works at the tennis, the person who works at the hotel. 

“Of course I also like winning matches, but this is a game and I know the opponent is sometimes — not many times — better than us. I love tennis, but I know it is not that important. If you think you are important because you are good at hitting a ball,” he concluded, while pointing a finger to his forehead, “you are not too intelligent.” 

Rafa has always had a knack for hitting a ball. He was four years old when Uncle Toni — who had ranked among the top 50 Spanish players in his early 20s — first put a racket in his hand. Until he was eight, this boy prodigy struck the ball double-handed off both wings. Then Toni came up with one of those “strokes of genius” that Wertheim’s book alludes to: he suggested that Rafa should hold the racket in his left — or wrong - hand. 

The justification? “I always hated playing lefties. I thought he should at least try it.” Toni was also responsible for Rafa’s extraordinary grip, in which he holds the butt of the racket, not the middle of the handle like the average club player.

The idea had grown out of Toni’s interest in table tennis, because this sort of grip increases your capacity for spin. As a direct result, Rafa’s wickedly hooked and weighty forehand has become the dominant shot in men’s tennis, calculated to rotate the ball at 5000rpm — or almost twice as fast as Roger Federer’s more conventional stroke. 

Toni, it seems, is no great believer in orthodoxy, whether in tennis or in life. He dislikes religion, arguing that “it comes from ignorance”. He has no interest in marrying his long-term girlfriend, pointing out that “if we are friends, you know it, I know it, and we don’t need to announce it. It is the same with my girlfriend.” At the same time, though, he preaches the importance of morality, humility, and above all, respect. Respect is a word he uses again and again.

“Rafael has never broken a racket, not once,” he said. “You should have respect for the money it cost, and for the people who made it. When you are at the computer and you type something wrong, do you throw the computer away? If you cannot control your body and your mind it is difficult to control the ball.”

It is hard to imagine a more loyal or committed supporter than Toni, who has given up his own life to steer his nephew through the shoals of superstardom. But he is far from being a fawning courtier. Even now that Rafa wears £350,000 watches, the nephew still has to put his expenses past his uncle’s watchful eye.

One story — quoted in Wertheim’s book - refers to an occasion in 2006 when the director of Queen’s offered to fly Rafa from Roland Garros to London by helicopter, only for Toni to veto the idea on the basis that he had already bought Eurostar tickets. “We’re not wasting that money,” he said.

When I brought this anecdote up, Toni was hazy about the details. He admitted, though, that it was the sort of thing he might have done. “You should always be equal with other people. I remember when Rafael was 16, and playing in Challenger events, he went out with a friend and told me the next day they had gone to a smart seafood restaurant. I said 'You’re 16! You should be eating at Burger King, like the other boys your age!’” 

But isn’t Rafael Nadal, the best tennis player in the world, entitled to a little luxury?

Toni fixed me with a stern look. “You can’t drive a Rolls-Royce all the time,” he said. “Look at Maradona, who came to London last year. He was so successful, but after football, there was a big fall. I say to Rafael, you might be No 1 or No 2 in the world, but it is better for you, I think, that you know how to be normal.” 

Ever the vigilant guardian, Toni is already thinking about his nephew’s exit strategy from the sport he has made his life. But with an ally like him in the player’s box, Rafa surely has many fine years and achievements still to come.