Aguero will be leaving the Etihad Stadium when his contract expires at the end of June, and Barca have allegedly already opened talks with the 32-year-old over a potential move to Camp Nou.
"Signing Aguero on a free transfer could be a coup for Barcelona," Rivaldo told Betfair. "He has a good relationship with Lionel Messi and, with Barca missing Luis Suarez this season, Aguero would probably go straight into the starting XI.
"But those players will cost big fees, so [head coach Ronald] Koeman should carefully weigh up the options before rejecting them, especially when we are talking about a player of Kun Aguero's quality."
Aguero is Man City's all-time record goalscorer with 257, but the forward has only managed three goals in 14 appearances during the 2020-21 campaign.