The Argentine striker has been sidelined since mid-December, having limped out of City's 6-3 win over Arsenal with a calf problem.
However, after missing eight matches in all competitions, the Argentine has resumed full training and could feature on Wednesday.
City boss Manuel Pellegrini said: "Sergio is working normally with the whole squad and he is in the squad list.
"He is a very important player for us. It doesn’t matter that we are scoring a lot of goals. Sergio will always will be an important player. We are very happy he is coming back."
Pellegrini will be forced to cope without David Silva and Yaya Toure against Blackburn, although the duo could return for the visit of Cardiff City at the weekend.
"David Silva and Yaya Toure are (out) with small problems," the Chilean added. "I hope they will be fit for Saturday.
"Yaya has the last two weeks played with a problem with his back, so it is a risk to continue doing that way. It is better for him to rest for two or three days."
