Rafael Nadal has a chronically injured left foot that sometimes hurts so much he cannot play.

A stress fracture in one of his ribs, suffered at Indian Wells in March, cut short his clay-court season and has left him with far less preparation than usual ahead of his favorite tournament, the French Open.

His knees are often on the edge of balky. He is two weeks shy of his 36th birthday, an age that, a generation ago, would have effectively stopped him from contending for, much less winning, Grand Slam titles. He limped through the final set of his last match, a three-set loss in the round of 16 at the Italian Open.

And yet, as Alexander Zverev, the world’s third-ranked men’s tennis player, watched Nadal practice Thursday morning — because even the best players in the world will stop and watch Nadal hit any ball at any time on the red clay of Roland Garros — Nadal’s vulnerability was not on his mind.

“Rafa, at this place,” Zverev began, then paused so he could properly explain what he thought he, his father and his coach had just witnessed, “all of a sudden his forehand is just 20 miles an hour faster. He moves lighter on his feet. There is something about this court that makes him play 30 percent better.”

Few would take issue with Zverev’s assessment. Nadal is 105-3 at Roland Garros. He has won 13 singles titles, the first coming half a lifetime ago, in 2005. He is the only player in the field with a 9-foot silver statue on these grounds.

“When we talk about favorites, for Roland Garros and clay, Nadal has to be right at the top,” Novak Djokovic, the reigning champion, said Friday.

For the first 10 weeks of the year, no one could beat Nadal. He won three titles and 21 consecutive matches (including a walkover) before the young American Taylor Fritz beat him at Indian Wells. But the wild swings of injury-induced inactivity and success have made Nadal as mysterious a presence in the field as he has ever been, and in his mind, hardly the favorite.

“For sure not, because the results say that I am not,” he said, before delivering a mysterious qualifier. “But you never know what can happen.”

He would not be here, he said, if he did not think he had a chance to win.

It has been a long time since Nadal showed up in Paris and this tournament was not his to lose. Nadal’s winning the French Open was long the closest thing to a foregone conclusion in this sport or any other.

In October 2020, with the pandemic having prompted the French Tennis Federation to move the tournament to early fall from late spring, Nadal stampeded through the competition without dropping a set. He embarrassed Djokovic, 6-0, 6-2, 7-5, in the final.

Nine months later, though, Djokovic got revenge, breaking Nadal’s spirit and his body during an epic four-set semifinal on his way to the championship. Mueller-Weiss Syndrome, the degenerative foot condition that Nadal has had since childhood, prevented him from playing for most of the rest of the year. For months during the fall, Nadal wondered whether he would ever play again.

Then the pain became manageable. And after just a few weeks of preparation and a single tournament, Nadal won the Australian Open in January, showing the world once more that counting him out is a terrible idea. But in recent days, the pain has been difficult again, and the top players can sense that the 2022 French Open has a different feel than others in recent memory.

“A lot of competition on the men’s side,” said Stefanos Tsitsipas of Greece, who lost the final to Djokovic last year after winning the first two sets. “It’s something that we haven’t seen for sure in a long time.”

Tsitsipas, 23, spoke of the “slightly younger and very hungry” players like himself, who are desperate to begin winning Grand Slams, and of Carlos Alcaraz, the rising and dangerous 19-year-old from Spain. “He seems like he plays tennis just because he enjoys the sport,” Tsitsipas said of the young Spaniard. But he prefaced those comments with a reference to Nadal, someone he jokingly described as having won the French Open “at least 28 times.” That is how large his presence looms on these grounds.

Nadal tried to downplay his prowess at Roland Garros on Friday.

He has collected dozens of championships on red clay throughout Europe, winning a dozen in Barcelona, 10 in Rome and 11 in Monte Carlo, so 13 at Roland Garros makes sense, sort of, he suggested. (No, it doesn’t. It’s ridiculous.)

Also, he said that the results from the last two months mattered more than titles won a long time ago. The rib injury made it difficult for him to sleep, much less swing a racket, especially with the violent torque that he generates on even his routine shots. Others, he said, have played so much more, and better.

Then again, Grand Slam tournaments, with their seven, best-of-five-set matches played over two weeks, are long affairs, especially on clay, on which points and matches stretch into attrition territory. The competitions are long enough for a player with a certain familiarity with the territory, who knows better than anyone what it takes to win tennis marathons, whose game is all about punishment, to catch up with those who are better prepared.

Then there is the additional motivation that Djokovic said every player gained when he showed up to compete for a Grand Slam title, an opportunity that awakened “so much emotion.”

“That is why you cannot underestimate anyone,” he said.

It is a rush of adrenaline that can make debilitating, even hobbling, aches and pains magically and mysteriously recede.

“Things can change quick,” Nadal said, though neither he nor anyone else can say with any certainty that they will. “Only thing that I can do is try to be ready if that change happens.”