Juan Martín del Potro hits tennis balls so hard it's a wonder they don't pop. He has a body that should make people nervous—6-foot-6, 214 pounds and muscular—but the heart of a golden retriever. In tennis, everyone loves him and hopes he's back for good.

After years of injuries, surgeries and heartache, the 27-year-old Del Potro is playing with joy at the U.S. Open. He's thrilled about winning a silver medal in singles at the Rio Olympics, where he shed many tears and beat top seed Novak Djokovic and former singles gold medalist Rafael Nadal. He loves how the Open has changed—a roof over Arthur Ashe Stadium, a new Grandstand court, practice courts with stands—since he last played here, in 2013. He's grateful for all the fans who cheer for him and ask for autographs. And he's touched by the words of fellow players, who don't want to lose to him, but know how much tennis suffers without him.

"I'm very proud of that because I think they admire what I've been through to get here," Del Potro said. "It's amazing all the love I receive from them.
Best of all: He's no longer afraid to say that he's starting to feel like the same guy who won this title, way back in 2009. Sport TV Channels

"It's like it was yesterday for me," Del Potro said. "In my mind, I'm still dreaming something big with tennis."

In 2009, Del Potro was a talented outsider, a gangly Argentine who was not seen as a player who would stand up to a champion like Roger Federer or Nadal in a marquee match. He reached the semifinals without beating anyone ranked higher than No. 17. Then he thumped Nadal—he lost six games total that day—and went up against Federer in the final. Federer, who had won the Open five consecutive years, won two of the first three sets. Del Potro won the last two in a stunner.


And then the pain came. His powerful shots made his right wrist ache, and rest and therapy did nothing. He had surgery and missed most of the 2010 season. After he recovered, his left wrist started to hurt. It has required three surgeries and cost him most of two seasons, in 2014 and. Last June, just before his third left wrist operation, he considered quitting. His surgeon, Dr. Richard Berger of the Mayo Clinic in Rochester, Minn., understood why.

"It's awfully discouraging for somebody of Juan Martín's stature to have to think about having yet another surgery," Dr. Berger said. "He knew that my bag was empty. I had no other arrows in my quiver that I could use surgically without running the risk of making things worse, from a scar standpoint, from an instability standpoint. This last operation was pretty much it.