Del Potro, who fractured his right kneecap last October, was scheduled to undergo tests on Wednesday.
He is set to meet Feliciano Lopez in the next round after the Spanish veteran rallied from a set down to beat Hungary's Marton Fucsovics 6-7(4) 6-3 6-4.
Frenchman Jeremy Chardy beat Mikhail Kukushkin 6-1 6-3 before rain brought matches on all courts to a temporary halt.
Rain caused the cancellation of a full day's play on Tuesday for the first time since the opening day of the 2012 tournament.
After action resumed a little before 1700 GMT, Swiss Stan Wawrinka sealed a comfortable 6-3 6-4 victory over local hope Dan Evans while qualifier Aljaz Bedene got past Alex de Minaur 3-6 6-4 6-4.
However, rain stopped play again with Stefanos Tsitsipas leading Briton Kyle Edmund 6-3 3-3 as the organisers pushed matches back to Thursday where action will begin at 1000 GMT.
(Reporting by Shrivathsa Sridhar in Bengaluru; Editing by Toby Davis)
