The controversial Italian striker was at his petulant worst again yesterday when he was substituted in the 55th minute of City's 3-0 victory over Sunderland.
The Sunday Mirror says there is growing pressure on Mancini to admit defeat in his attempt to unlock Balotelli's potential.
The club's Abu Dhabi-based owners are fearful that Balotelli, who arrived in a £24million deal from Inter Milan two seasons ago, is damaging the City brand with his indiscipline both on and off the pitch.
A City insider confirmed: "Mancini has staked his reputation on Balotelli, but every time he thinks he has turned the corner he does something else to land himself in trouble.
"Mario's a source of friction both in the boardroom and the dressing room."