Confidence is crucial for any athlete, but especially a tennis player. After all, he or she has no one else to turn to. The place to look is always inward. It’s existential. Tennis players call it belief, and they talk about it, mostly to themselves, all the time.

Different players draw on different things to develop and sustain belief. Maybe it’s faith in one shot (a big first serve, say) or an aspect of temperament (patience, for instance) that they bring to the court. For Rafael Nadal, it has always been about his body. As a child, under the tutelage of his uncle Toni, who would eventually coach him to greatness, Nadal worked at being stronger and more physically fit than anyone he would face across the net. As he says again and again in his autobiography, “Rafa,” written with the El País journalist John Carlin, he reasoned that his willingness to train relentlessly would help him to quiet his mind in tense moments and to fend off weariness in those long Grand Slam matches he so wanted to win. Being “in perfect shape,” as Nadal puts it in the book, would also, as he doesn’t say, compensate for the unorthodox mechanics of his ground strokes and his grinding style of play.

Fifteen months ago, I wrote that Nadal was pretty much out of belief, and fading. I was right, diagnostically. He was losing to lesser players. His body was showing signs of slowing down and breaking down and would soon break down further: an injury to his left wrist, his hitting wrist, forced him to withdraw from last year’s French Open and to miss Wimbledon. When he returned briefly at summer’s end, his play was lackluster. But I was dead wrong in my prognosis. Nadal, who turned thirty-one earlier this month, has, like his thirty-five-year-old frenemy, Roger Federer, summoned an earlier self. He’s reëstablished his body and his belief, and, remarkably, is playing like it’s 2008.

At Roland Garros, on Sunday, on la terre battue of Court Philippe Chatrier, where he’d won nine previous French Open titles, he won his tenth, which is four more than the second-best dirt-player ever in the men's game, Björn Borg. Culminating one of the most dominating clay-court seasons of his or anyone else’s career, he crushed Stan Wawrinka in straight sets, 6–2, 6–3, 6–1, and, truth be told, it was more lopsided than even that score line suggests. It was such in each of Nadal’s wins in Paris over the past two weeks. He lost only thirty-five games during the entire tournament, and didn’t drop a set, losing four games in a set only three times. I watched each of his seven matches, and I don’t think I’ve ever seen this great play greater.

When it comes to tennis, belief can be observed and measured, starting with the serve, where a lack of confidence tends to produce faults, a drop-off in pace, and a despair that seeps into the rest of a player’s game. Nadal’s first serve has never been a potent weapon—he doesn’t crack a lot of aces—but not since the U.S. Open in 2010, when he adjusted his grip to create a bit more pace, has he served as well as he did at this French Open. He struck first serves approaching a hundred and twenty miles per hour, five per cent faster than his average, and hit a wider variety of spots than he traditionally has. These changes, according to Nadal, came at the prompting of his new coach, the retired Spanish tennis star Carlos Moya. It’s a standard ploy for a left-hander, like Nadal, to slice serves out wide in the ad court when facing a righty. But numerous times during the tournament, and especially at key moments during his semifinal trouncing of the rising young Austrian Dominic Thiem—the second-best clay player on the men’s side this season—Nadal instead served up the T, catching Thiem, like he’d caught others, leaning left. He earned cheap points with service winners, and even hit a few aces.

Nadal’s second serves were ridiculously effective, too. It’s a good day on the A.T.P. tour when a player wins a little more than half the points off his second serve. According to Craig O’Shannessy, a tennis strategist who runs the Web site Brain Game Tennis, Nadal, in his first four matches in Paris, won seventy-seven per cent of the points that began with his second serve. He mauled the top-twenty player Roberto Bautista Agut in the fourth round by a score of 6–1, 6–2, 6–2; by the end, his opponent looked pained and even frightened to be receiving.

Nadal always serves with the intent to hit the next shot with his forehand. He has essentially had one strategy since turning pro, at fifteen, in 2002. Against right-handers, he ceaselessly attacks the backhand, wearing it down with his heavy topspin forehand. When he was in his doldrums last year, he was hitting his forehand tentatively, and it wasn’t producing the depth it needs to be effective. During his French Open run, Nadal swung freely and fiercely—another sign of belief—creating absolutely sick topspin with that low-to-high, lasso-finish forehand of his. The ball was clearing the net by feet, then swooping down to land deep in the backcourt, often brushing the tape at the baseline. On clay, and especially on the dry, sunbaked clay at Roland Garros this year, the high bounce that Nadal’s topspin created forced his opponent into a handful of bad choices: either stand the ground just behind the baseline and take the ball shoulder-high, from where little topspin or power can be generated; step in and take the ball on the rise, a difficult shot to time; or retreat and wait a bit for the ball to descend from its bounce, a tactic that bought Nadal time and, too often, resulted in a return left short for him to pounce on.

And pounce he did. Nadal tends to position himself eight or ten feet behind the baseline, confident that his quickness will get him to drop shots and his toughness will carry him through the long rallies he creates with his defense. But he won a lot of rallies of eight shots or fewer by stepping inside the baseline and redirecting balls down the line from both his forehand and his backhand wings. To redirect a tennis ball, you have to believe; to dare to redirect a ball down the line, over the highest part of the net with the smallest margin for error, you really have to believe.

Everything that had worked for Nadal throughout the tournament worked for him the final, starting with the mid-afternoon weather, which was hot and sun-bleached—just the way he likes it. He began with a hold at love, and continued to serve with conviction and variation, keeping Wawrinka off balance and forcing him to settle for simply blocking returns back, rather than stepping in. Warwrinka saw only one break-point opportunity during the entire match, in the third game of the first set, and he failed to convert, shanking a backhand badly. You heard the clang of ball meeting frame, and not for the last time.