Lopez, who still plays on tour but is now the event's tournament director, issued an announcement on social media.
"I spoke to my friend Rafael Nadal, who confirmed his participation in Madrid," he said, adding that he would be received with ''open arms" at the tournament.
He hablado con mi amigo @RafaelNadal y me ha confirmado su participación en Madrid el próximo mes de septiembre! ❤️ ¡Te esperamos como siempre con los brazos abiertos en la Caja Mágica! pic.twitter.com/ZWywVEQstO— Feliciano López (@feliciano_lopez) July 7, 2020
The rescheduled clay-court event is currently slated to be played the week following the US Open.
That casts doubt on whether Nadal plans to compete at Flushing Meadows, where he is the defending champion. The 34-year-old Spaniard had previously described conditions as "not ideal" for having the tournament.
"Right now I wouldn't want to go play a tennis tournament in New York. But I don't know in two months," he said a month ago.
Nadal, in addition, has back-to-back titles to defend at Rome and French Open, which follow Madrid in the reshuffled schedule. It is generally expected that most top players will choose not to play all events to give themselves time to rest and retrain as they return to tour.
But Nadal will be helped by the ATP's ranking adjustments, which will allow the 19-time major champion to keep the points he earned during his title runs at the above events in 2019, regardless of whether he plays them this season. Players will not be able to count the same tournament twice in their point totals.