There will never be another tennis player like Rafael Nadal

When Nadal exploded into tennis 20 years ago, his game appeared too physical, too muscular, too hard on the body to survive for very long.

Tennis is a game of fluidity and grace, but the teenage Spaniard played it like he was moving a piano by himself. Nadal didn’t hit. He heaved. He didn’t run—he charged. He hit a semi-Western grip forehand with a wild spin, finishing with a lasso-like flourish, and his backhand was a deep, grunting scoop.

His high-effort talent was a marvel, great enough to win the French Open at age 19, but it couldn’t last.

It lasted. Longer than anyone imagined. “More than I ever believed possible," Nadal said Tuesday in Spain, finally stepping away from the sport at age 38, after a Davis Cup singles loss.

His style indeed proved pounding: Nadal endured repeated injuries over his two decades, some substantial with long delays, but he always found his way back to familiar, brilliant form. Nadal won 22 major titles, an absurd 14 at the French, two Olympic golds, and he played some of the most objectively high-level tennis of all time.

No longer. Nadal’s whole body said: stop.

He is such a one-off he’s hard to explain. Ask yourself this: Who plays tennis like Rafael Nadal? It isn’t difficult to find youngsters trying to imitate Roger Federer’s one-handed backhand, or Novak Djokovic’s sliding baseline chops, but imitating Nadal is hopeless. Who has the time or endurance? The physicality, the outrageous spin, the power strokes, the dedication to hit that way again and again…all of it by a natural righty who learned to hit left-handed, it’s an impossible standard. It’s like telling a kid to grow up and be the Hulk.

Of course, what wound up defining Nadal’s tennis career was not the body, but the heart. Pick whatever cliché you want: it was three sizes too large, he wore it on his sleeveless sleeve…Nadal has a case as the hardest out in tennis history. He gave everything, always. He took no points off; he didn’t reset to a B game. As long as he was standing, he was still in it.

Botic van de Zandschulp of the Netherlands, who beat Nadal Tuesday, will probably have lifelong nightmares in which Nadal roars back to catch him in a tiebreak.

Always the sportsman warrior, Nadal took his final defeat with class. He could be a brute with the racket, but he was polite to opponents, and respectful to the game. He became wildly famous, as big as any Spanish athlete ever, and he never carried himself as larger than the sport. He stayed humble, expressed doubt, celebrated but never gloated. He was graceful in loss and triumph. Nadal would occasionally bicker with a chair umpire, but his go-to weapon was a death stare.

This is the formal end of the Big Three. Of course, it ended a couple of years ago, with Federer’s retirement, but it really ends here, because Nadal vs. Djokovic still felt like a version of it, and now that’s over, too. Tennis fans are still processing it, this comical pot of gold that landed in their laps, a trio of legends with contrasting styles who elevated each other into greatness. The tangles were epic. Nadal ended at 24-16 lifetime versus Federer. Djokovic edged him, 31-29.

Those margins don’t do the rivalries justice. What we recall most are scenes: a victorious Nadal in the Wimbledon twilight in 2008 next to a teary Federer, an exhausted Nadal and Djokovic propping their weary bodies up against the net at the end of the 2012 Australian Open after Djokovic’s 5 hour, 53 minute win—the longest major final of all time.

All three men are intertwined, forever. Federer published a lengthy farewell Tuesday, thanking Nadal for raising his game—changing it, really, because Nadal’s high bounce forehand threatened to swallow him whole. He ribbed him gently about all his little tics, from the way he arranged his water bottles “like toy soldiers in formation" to the constant picking at his shorts.

“Secretly, I kind of loved the whole thing," Federer wrote.

It was hard not to. Nadal’s habits may have been a quirky package, but the player commanded respect. The legacy is immutable. Some will argue the 14 French Open wins somehow devalue the 22 overall majors, but it’s a silly position—as if he collected an easy 14 titles at his backyard pro-am. His dominance on a difficult surface isn’t his dilemma. Nadal played ferociously wherever he played.

I get the feeling he doesn’t care. In interviews, Nadal had little interest in the all-time talk. That was for others to figure out. On Tuesday he said he wanted to be remembered as “a good person from a small village in Mallorca." He spoke of his fortune to have a tennis coach for an uncle, Toni, and this was very Nadal: an acknowledgment he hadn’t done it all on his own. Surroundings play a role, even for the best.

“Many people work hard," Nadal said. “Many people try their best every single day. I was very lucky."

He leaves the game in an improved place. He even has a spiritual heir: the 21-year-old Spanish right-hander Carlos Alcaraz, another humble kid from a small village. Alcaraz, who has already won four majors, grew up worshiping Nadal—one of the more adorable sights this season was Alcaraz following Nadal around like a puppy during the Paris Olympics, desperate to give his idol a final hurrah.

Alcaraz wisely doesn’t imitate Nadal’s strokes, but he plays with similar, swashbuckling relentlessness. No tennis point is ever over. It is a passionate tribute, though Alcaraz knows what everyone does: Rafael Nadal will not be repeated.

Write to Jason Gay at Jason.Gay@wsj.com