Chris Trotman/Getty Images Del Potro made the rounds of the talk-show circuit Tuesday morning.

On Monday, Juan Martin del Potro won the U.S. Open. Tuesday morning, he watched himself do it again and again, as if to prove that it really happened.

“On TV, on the Internet, everywhere,” del Potro told a small group of reporters in midtown Manhattan. “When I saw the ball going out, my sensation—it’s amazing, I can’t explain with words.”

It was easier for del Potro to explain how he felt after a sleepless night on the town, mostly at Avenue, a posh club on Manhattan’s West Side.

“I don’t want to play for a while,” he said. “I need the rest.”

Winning a major title for the first time is a transformative moment in any player’s career. In the 20-year-old del Potro’s case, the victory seemed to have physical effects, too. There he was on Monday, sporting a scruffy beard and a sleeveless shirt as he mowed down Roger Federer with booming forehands. On Tuesday, he looked more like a GQ model, dressed in stylish jeans, a pressed collared shirt, and a sweater. He visited with the Today Show hosts, Regis and Kelly, and Charlie Rose.

Del Potro isn’t attracting all this attention just because he beat Federer, the five-time defending U.S. Open champion who was on a 40-match winning streak in Flushing. It’s how he did it that was most impressive. After a nervous and tentative start that seemed to doom him to a quick defeat, Del Potro gathered himself midway through the second set and began to play with emotion and poise. He charged back from a two-sets-to-one deficit, going for bigger and bigger shots as the match became increasingly tense. When Federer was two points from winning the match, del Potro refused to fold.

“When I started the fifth set I said [to myself], ‘It’s kill or die,’” he remembered.

It’s an attitude that few players have had against Federer, who is revered by his colleagues, often to the point where they are unable to perform while on court with the all-time major titles leader. Del Potro’s approach was so different, so powerful and fearless, that it has left the tennis world giddy at the prospect of another talented, tough-minded athlete to share the stage with Federer and Rafael Nadal, who had combined to win 20 of the last 23 Grand Slam singles titles before Monday. Del Potro said he appreciates the praise, but isn’t quite worthy of that comparison just yet, even though he defeated them in back-to-back matches on his way to the title.

“[Federer and Nadal] are much better than me at this moment,” he said. “But I’m working to improve and to close the difference between them and me.”

First though, del Potro has to plan a celebration. Step one: Return to Argentina Tuesday evening. Step two: Gather his family and friends in Tandil, his hometown, and let loose. How loose?

“I don’t know,” del Potro said. “But crazy, for sure.”

Del Potro’s parents and sister do not travel with him to tournaments, but they did watch his victory on television. His father, Daniel, was a semi-professional rugby player and is now a veterinarian, and his mother, Patricia, is a teacher. Del Potro spoke to them after the match.

“I just say, ‘Hello,’ and then we start to cry,” he said. “Was difficult to speak.”

Tom Perrotta is a senior editor at TENNIS magazine. Follow him on Twitter.