The enigmatic front man was left out of the City squad last week as they ran out 2-1 winners over Tottenham at the Etihad Stadium.
Mancini and Balotelli have had a relationship of seemingly tough love in the past, with mixed results. But the defending champions' boss has revealed that the Italian was dropped against Spurs because of poor performances in training.
"I told him this was the reason - because he didn't work well for three days," he told reporters.
"I think Mario needs to work harder. If any player doesn't work hard it is difficult that he can play at this level.
|9/2||Mario Balotelli is 9/2 with Paddy Power to score the last goal against Aston Villa|
The 21-year-old Italy international is yet to score in the league this season, but has scored in the Capital One Cup and netted a vital last-minute penalty against Borussia Dortmund in the Champions League.
With crunch games on the horizon, Balotelli will be expecting minutes on the field, although there has been speculation in recent weeks that the striker could be on his way out of the club.