Nadal is the defending US Open champion, but has previously expressed concerns about travelling to the tournament amid the Covid-19 pandemic.
The hard court Grand Slam runs from August 31 to September 11, while the re-arranged Madrid Open, played on clay, is scheduled from September 12-20.
Madrid Open tournament director Feliciano Lopez tweeted: “I talked to my friend Rafael Nadal and he has confirmed his participation in Madrid next September! We wait for you as always with open arms in the Magic Box.”
Nadal responded with: “That’s it Feli. See you in Madrid in September. Meanwhile everything goes well.”
The Madrid Open is one of two Masters clay events leading up to the French Open, which Nadal has won 11 times and runs from September 27 to October 11. There is also the Rome Open from September 20 to 27.
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Nadal’s uncle Toni said last month that the new ATP schedule was challenging.
“It is difficult in a month to do the US Open, Rome, Madrid, and Paris. It is almost unfeasible,” he told ESPN.