“Do you fear your body?” I ask Juan Martín del Potro. The 6’6” Argentinian looms over me like a lamppost. He’s silent for a moment. He knows I’m really asking him: Are you afraid the pain will return?

Nine years ago, del Potro was at the top of the tennis world. He beat Rafael Nadal and Roger Federer back-to-back to win the 2009 U.S. Open and looked poised to take many more titles. But a string of injuries kept him off the court for years, turning that hope for the future into a parable of potential loss. But this is del Potro’s second act. In 2018, he’s played some of his best tennis to date and has returned to the top of the rankings. He's currently third, just behind—you guessed it—Nadal and Federer.

He looks at me, thinking about my question. His face is shaded by thick stubble. Some players his height are so lean they look almost scrawny, but del Potro’s frame is solid, broad. His impossibly long limbs look like thick ropes, propelling him forward with fluid strength as he leads me from his hotel lobby out to a sunny courtyard that overlooks Miami’s Biscayne Bay. We sit at the water’s edge, but he keeps his back to the stunning view. Behind us, south across the bay, the men’s final of the Miami Open Masters has just begun.

“I don’t fear my body anymore,” he says, finally. “But I’m tired. It’s a big challenge for me to stay healthy for the entire year. And that’s the most important thing—to just be able to play tennis.”

A few days prior, there had been a scary moment in his match against Milos Raonic. Del Potro was chasing after a ball midpoint and fell full speed off the court and into the photographers' pit. He stayed there for a minute, doubled-over, his face hidden. The crowd gasped and then stood silent, waiting, fearing the worst. Someone sitting near me in the stands incanted in a whisper: “No no no no no, don’t let him be hurt, not again.” But del Potro finally emerged from the pit and returned to the line and, shakily, continued playing, narrowly winning the match.

In a sideline interview, Raonic’s coach, Goran Ivanišević, dismissed del Potro’s extended stay in the photographers' pit as mere theatrics. “Del Potro is acting like he is injured. Walking slowly. He is a master of doing that. Did that at Indian Wells as well, against Milos.”

When I mention Ivanišević’s assessment, del Potro grimaces and shakes his head. “I’ve never done a fake injury or something like that. If I look tired, in pain, it’s because this is true. I have to do two or three hours of treatments every day just to be able to step onto a tennis court. My body is really worn out. This pain is part of my life, and I play the match with it. And since no other player has gone through what I’ve gone through in terms of injury, setbacks, it’s hard for them to understand.”

Doubts like Ivanišević’s stem from the fact that del Potro’s game embodies some disorienting contrasts, so much so that watching him play is, at times, an exercise in cognitive dissonance. He walks the court with slow, languid strides, somehow looking both exhausted and elegant. He strolls to the baseline and then, when the point begins, suddenly he’s leapt to meet the ball with a speed and agility that should be impossible for a man his size. His exceptional movement allows him to get to shots that should have passed him; his balance when hitting a running forehand allows him to turn defense into offense instantly. He not only makes it to the ball but often returns a blistering winner of his own. He leaves his opponents in disbelief, looking back at him as if they’ve been tricked.