"I think this is the best moment of my life," del Potro said.
Nadal was dealing with a strained abdominal muscle, which after the match he finally admitted was bothering him. The six-time Grand Slam champion also gave plenty of credit to del Potro, who deserved every bit of it.
"Just have to congratulate him," Nadal said.
The sixth-seeded Argentine - first from that country to make a U.S. Open final since Guillermo Vilas in 1977 - kept No. 3 Nadal pinned behind the baseline with a deep, flat forehand and a first serve he mixed at between speeds in the 90s to the 130s.
In the first set, Nadal put on his usual show, battling for every point, never giving in, even though it appeared he was being overpowered. The first four games took 27 minutes.
But he couldn't convert any of the five break points he had against del Potro's huge serve over the first 12 games. And there was no waiting out this storm, no hoping del Potro might weaken, the way he did earlier this year at the French, when he was leading Roger Federer 2 sets to 1 at his first Grand Slam semifinal.
Federer came back in that one and might await again. In the final, pushed to Monday because of rain over the weekend, del Potro will play either Federer or Novak Djokovic. His record against the two: a combined 0-9.
The result prevented the eighth Federer-Nadal final in a Grand Slam and first at the US Open. It also kept Rafa stuck on six major titles and still in need of the US Open to complete the career Grand Slam.
"I'm sorry," del Potro told the crowd in his on-court interview. "But tomorrow, I'll fight until the final point for you, for everyone, to show good tennis."
