Considerable speculation inevitably accompanies wealthy City into any transfer window but this time the main movements could be outgoing.
City are looking to offload absent striker Carlos Tevez while defenders Nedum Onuoha and Wayne Bridge, both surplus to requirements, are also available.
The club have already held negotiations with AC Milan about Tevez but have not yet reached an agreement as their hope is for an immediate sale while the Italians want to loan the player first.
Mancini believes a deal could be done quickly if Milan agree to their terms but he says other clubs are also interested.
The Italian said: "We need to sell three or four players and with Carlos we could close (a deal) with a club in the next three or four days, and also possibly Wayne. Then maybe we can do something.
"We hope for us and for Carlos we can do a deal. There are two or three teams in Italy, a team in France, and another team involved - I hope for him he can start to play football.
"We could maybe bring someone in, but we need to sell."
The absence of Tevez, City's top scorer for the past two seasons, for much of the campaign has left the club a striker down but Mancini is not necessarily looking for a direct replacement.
Mancini feels he has enough firepower and is more likely to target a midfielder with key man Yaya Toure soon to depart for a lengthy spell on international duty.
Mancini said: "We have three strikers, plus Samir (Nasri), David (Silva) and Adam Johnson. Maybe we need one midfielder if we can do it."
City have been linked with Roma star Daniele De Rossi but Mancini does not know if a deal for his fellow Italian is feasible.
He said: "De Rossi is a top player, like Yaya, but he plays for Roma, a top team, and he was born there. I don't know if he will leave."
City hope to have striker Mario Balotelli and midfielder Nasri back for Sunday's eagerly-anticipated FA Cup third round clash against Manchester United.
Both pulled out of the Barclays Premier League leaders' win over Liverpool in midweek through illness.
Mancini said: "Samir was ill, Mario the same. I hope that they will be okay for the game against United.
"They trained with us in the morning but then were ill."