Del Potro's dream run at the Games continued with a 5-7 6-4 7-6 (7-5) victory over Nadal on Saturday setting up a meeting with defending champion Andy Murray in the decider.
Rio 2016: No excuses from Nadal after Del Potro loss
Rafael Nadal refused to use fatigue as an excuse after losing his men's singles semi-final to Juan Martin del Potro at the Rio Olympics.
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Nadal's busy schedule has included winning gold in the men's doubles on his return from injury.
But the Spanish 14-time grand-slam champion was unwilling to use that as an excuse, saying: "Now is not the time to talk about being tired.
"I gave the last drop of energy I had to try to win another medal."
Nadal, who will face Kei Nishikori for the bronze medal, paid tribute to Del Potro.
"It was a great match. I fought until the end, I gave my best effort. After a tough week, a lot of matches, it's tough to be at your 100 per cent, but I did," he said.
"And I cannot say anything else. Just congratulations to Del Potro. That's it; I did my best."
Del Potro beat Novak Djokovic in the first round and his run has taken him into the final, much to his surprise.
"It's so nice. I cannot believe it," the Argentinian said.
"I am living a dream. I don't want to wake up from this.
"I didn't expect to be in the finals, to get a medal, and even beating Djokovic and Rafa. I am so glad with my success in this week."
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