Aguero, who has missed the last five games with a hamstring injury, returned to training earlier this week with an eye on a comeback against Sunderland at Wembley.
His potential inclusion gives City a huge lift with the Argentina striker having scored 26 goals this season before limping out of the 5-1 win at Tottenham on January 29.
Manuel Pellegrini, speaking at his pre-match press conference, said: "Of course it is very important for the team to have Sergio again with us because he is a very important player."
The City boss, however, would not confirm whether the Argentina striker would be fit enough to start.
He said: "It is something I must decide from Saturday, and see the way he recovers from the work this week, if he is 100 per cent fit after his injury, to play the whole match."
Fellow forward Stevan Jovetic, who has had little luck since joining City in a B£22million move from Fiorentina last summer, has been ruled out.
The Montenegro international came off the bench during last week's Barclays Premier League win over Stoke only to go off again with a hamstring problem.
Defender Matija Nastasic, who has missed four games with a knee injury, is also out.
Pellegrini has used squad players such as Costel Pantilimon and Joleon Lescott in the earlier rounds but gave away no clues as to whether they might again feature.
He said: "It is not easy to choose the 11 starters, all the players deserve to play.
"I will try to choose the best 11 starters for this team as I did in all the other games."
- Sports & Recreation
- Manuel Pellegrini