Dimitri Seluk claims City have not made Toure feel valued and appreciated, especially on his 31st birthday which clashed with a party in Abu Dhabi to celebrate City's title triumph.
Seluk told The Sun: "There's a big possibility Yaya will leave this summer
"What happened at his birthday meant the club don't care about him
It was proof
"In a normal team, his team-mates and club would at least give him good wishes
"He's very upset and he started thinking of leaving the club
And he will leave if things carry on like this.
"It's not a question of money or contract, believe me
He has everything he needs
For Yaya what is the most important thing is human relationships.
"When your best worker has his birthday from time to time it's not bad to shake his hand
To make him feel valued and appreciated
They don't give any attention to Yaya."
Toure signed a new four-year deal with City last season.