"If you’re not excited about the U.S. Open, you’re not a tennis player," Nadal told reporters.
Injuries are affecting several top players heading into the last grand slam of the year in a season made even more hectic with the Olympics squeezed into the schedule.
Men's top seed Novak Djokovic, like Nadal, is also dealing with a wrist injury and women's number one Serena Williams is coping with a sore right shoulder.
Lefthander Nadal, sidelined after being unable to play his third-round match at the French Open because of an injured left wrist, decided to test himself in Rio.
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"I was two months and a half outside of the competition, and not only outside of the competition, outside the practice courts. I couldn't practise," the Spanish fourth seed said at Flushing Meadows on Friday.
Nadal, 30, said he was determined to give it a try in Rio and ended up feeling good enough to compete in singles, doubles and mixed doubles.
"The motivation, the passion, sharing moments with the team helped a lot," said Nadal, who reached the Rio singles semi-finals and won gold in doubles with his friend Marc Lopez.
"Winning a gold medal is always something unique, and I think I enjoyed it as much as I can during the whole event," he said.
"I finished the tournament completely exhausted ... no more energy inside of my body."
Nadal carried on straight from Rio to Cincinnati where he won his opening match before losing to teenager Borna Coric of Crotia.
"I am better, I am a little bit better," said Nadal. "It's true that the wrist bothers me a little bit less every day. I need to understand again to hit my normal forehand. During the wrist injury, always you try to find movements to avoid the pain.
"Today I can start the forehand, I think my normal forehand, but still needs time to feel that I am more confident on my wrist. But I am practicing well and I am competing well."
Nadal hopes his Rio elation carries over to the Open, which he won in 2010 and 2013.
"I have been playing at a very high level. So that helped me to play well in the Olympics, and I hope it's going to help me to play well here," the 14-times grand slam winner said.
"When you go to the Olympics and finally you win a medal, it's just the most important thing that you can do. So I'm just very happy for that, one medal for my country."Nadal will play his first-round Open match against Uzbekistan's Denis Istomin, who reached the fourth round in New York in 2012 but is 7-20 this season.
(Editing by Andrew Both)
