"I just wanted to tell you I'm so excited to come back to Argentina to play my good friend Juan Martin del Potro at Parque Roca," Federer said in a video on Del Potro's Twitter account.
The Parque Roca stadium has a capacity of around 15,500 and is primarily used for Davis Cup ties.
Del Potro, the 2009 US Open champion from Argentina, has not played since fracturing his right knee in the Wimbledon tune-up at Queen's in June.
The injury-plagued 30-year-old was forced to miss this year's US Open after finishing runner-up to Novak Djokovic in the 2018 final.
He is expected to make his comeback at the ATP tournament in Stockholm, which runs from October 14 to 20, and is also scheduled to compete in Vienna the following week.
The match in Buenos Aires will take place at the same time as the revamped 18-team Davis Cup finals, to be held in Madrid from November 18 to 24.
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