Mario Balotelli will fly to Milan on Wednesday to complete his transfer from Manchester City as new details emerge of why Roberto Mancini decided it was futile to continue believing the striker would stop letting him down.

Mancini's patience finally snapped because of the events leading to the late and dangerous challenge on Scott Sinclair that led to the embarrassing series of photographs showing City's manager grappling with Balotelli at the club's training ground on 3 January.

Twenty-five minutes before that training session, Mancini had summoned Balotelli for a heart-to-heart in which he tried to convince the player that he still believed in him and was certain he could be one of the key players in a successful title defence. "This is your chance – don't waste it," he told the Italy international.

What followed was so reckless that it convinced Mancini he was fighting a lost cause and that the colleagues who had advised him to give up on Balotelli were correct. His anger was evident for all to see in the pictures of the flashpoint.

Mancini still has strong reservations about letting Balotelli go without having a replacement lined up, preferring an end-of-season deal rather than leaving City with only three established strikers. Privately, however, he had accepted a club with City's ambitions could no longer afford to carry someone so unpredictable.

The only reason he had said he wanted to give Balotelli another chance, or "100 more chances", was an old managerial trick based on City being aware that advertising he was available would drive down the transfer fee. Behind the scenes, all the relevant people have been making plans for his departure for the past fortnight. It is understood the transfer to Milan is worth £17m, rising to £19.5m depending on how Balotelli does at San Siro.

Mancini, it has also emerged, had told Balotelli that he should think about changing the company he was keeping in his social life. Mancini did not think it was so bad when his own son, Andrea, lived in Manchester but the nature of Balotelli's hangers-on has increasingly become a concern. He had also told the player he should travel to Italy to spend time with his baby girl as part of leading a more grown-up lifestyle. To Mancini's dismay, he came away believing the 22-year-old was not particularly willing to listen to his advice.

Until 3 January, however, Mancini had been willing to forgive Balotelli for his erratic form and recurring ability to attract headlines for the wrong reasons, retaining his faith in the striker despite him playing an increasingly peripheral part this season, with only one Premier League goal.

Elsewhere, there has been a feeling behind the scenes at City for over a year now that the club would be better off off-loading someone who was underperforming so regularly and bringing in a superior replacement. Mancini is an admirer of the Napoli striker Edinson Cavani and a summer move is possible.