The Argentine has been sidelined with a knee injury since the Premier League champions’ opening-day victory over Southampton, and was not risked for Saturday’s 1-1 draw with Stoke.
Despite concerns still remaining over Aguero’s fitness, Mancini is set to gamble on the 24-year-old making a full recovery in time for Tuesday’s tie, and even hinted at a possible start at Santiago Bernabeu.
"I think he can have a chance," Mancini said. "Sergio will travel with us.
"He worked with the team in the last three days before the Stoke game. We didn't want to take any risks with him - but maybe he can be ready for Madrid.
"Will he start? I don't know."
Another player who has overcome a troubled start to the campaign is Gareth Barry, who returned to first-team action as a substitute at the Britannia Stadium.
"I'm happy for Gareth after three months to play again," added Mancini. "It's important for us because he's an important player and he had 30 minutes and did well."