Balotelli's extraordinary, controversy-filled spell at the Etihad Stadium came to an end this week as he completed a reported £19million transfer to boyhood club AC Milan.
The move came at the end of a month of intense speculation over the fiery striker's future, which City had consistently downplayed, but ultimately it was felt the deal was in everyone's interests.
Mancini, who expressed his sadness at the 22-year-old's impending departure earlier in the week, said: "We are not happy because I think he did well.
"Maybe not in the last three or four months because he had a big problem with injuries, but he did well because he helped the team win the Premier League and the FA Cup.
"We are sad for this but this is football.
"It was difficult, it was only my decision.
"I am here, (for) the club and Mario. Also for Mario to go back to Italy to play for Milan was important.
"I believe in him and I believe to go back to Italy after two years in England is important."
- Sports & Recreation