Juan Martin del Potro, who last played in March 2019, lost 1-6, 3-6 to compatriot Federico Delbonis in the first round of the Argentina Open.
Juan Martin del Potro defeated Rafael Nadal and Roger Federer in the same Grand Slam to win the US Open in 2009.
Juan Martin del Potro has not played professional Tennis since 2019 due to a string of knee injuries.
The Olympic silver medallist Del Potro has been out of competitive action since 2019. He has undergone three knee operations in that period.