City boss Roberto Mancini substituted the 20-year-old striker after a trick backfired in a pre-season game against Los Angeles Galaxy.
"I've played with some strange characters in the past but it's the first time I have seen that," De Jong told The Guardian after the game.
"It is frustrating, and he has to iron out those issues otherwise it will be a waste of his talent. He has to realise that now.
"All his teammates are here to help him but he's his own person and he is the only one who can change his ways."
City drew 1-1 with Galaxy but beat them 7-6 on penalties in the World Football Challenge.