Balotelli is now an AC Milan player after completing a move reportedly worth £19million, rising to £22m.
Mancini worked hard to coax the best out of the enigmatic Italy international during his extraordinary, headline-grabbing spell at the Etihad Stadium but ultimately accepted a move was in everyone's interests.
"We are very sorry for him because he leaves the club but we hope Mario can continue to improve and continues to work hard because he is a top, top player," Mancini said.
In truth -- on recent evidence -- Balotelli may not be greatly missed having scored just three goals all season, only one of them in the Premier League. He had also made only two substitute appearances since a dismal display in the derby loss to Manchester United on December 9.
Prior to Tuesday's goalless draw at QPR, City had been hitting their best form of the campaign with six successive wins in all competitions.
With no replacement for Balotelli signed before the transfer deadline, it is thought reserve striker John Guidetti could soon be promoted to the senior squad. The 20-year-old Swede made a big impression on loan at Feyenoord last season but has missed most of this campaign with a leg injury. He is now getting close to fitness and City reportedly turned down deadline-day approaches for the player.
City did sig 18-year-old Ghanaian striker Godsway Donyoh from his country's Right to Dream Academy and immediately loaned him to Swedish club Djurgarden.
Meanwhile, Balotelli wasted little time settling into his new surroundings in Milan. Balotelli formally signed a four-and-a-half-year contract with the Rossoneri in the morning and then made a goalscoring appearance in a friendly against Darfo Boario.