Manchester City defender Jerome Boateng is to undergo knee surgery and could out of action until the final two games of the Premier League season.
Boateng sustained the knock while on international duty with the Germany last week and Mancini revealed the full extent of the blow ahead of Sunday's match against Sunderland.
Mancini said: "He will have surgery in the next two or three days. Maybe he will be fit for the last two games."
There was more positive news coming out of Eastlands regarding Micah Richards. Mancini said he was hoping that the defender, who suffered a hamstring injury last week while with the England Under-21 team, will be fit in time for the semi-final clash with rivals Manchester United at Wembley on April 16.
"We are trying to get him fit for the semi-final. I don't know if it is possible but we hope," said Mancini
The twin problem, coupled with Kolo Toure's continued absence following his failed drugs test, leaves City struggling for defenders ahead of the visit of Sunderland.
At least Pablo Zabaleta has returned after flying back to South America to visit his ill father.