Roberto Mancini urged Samir Nasri to become more consistent, and has told the Frenchman he has the potential to win every game he plays in.
Nasri was shortlisted for the PFA Player of the Year award in the 2010-11 season, his final year at Arsenal, but has only produced that form intermittently for City.
The £24-million man made a brilliant City debut against Tottenham in August 2011, when he was involved in four goals, and scored against Spurs and Chelsea in the second half of the season to help them win the title.
But he only finished the year with six goals and after beginning the current campaign with two goals in as many games, his performance level has dipped again.
And Mancini said: "In my opinion we are talking about a top, top player here. And if he wants he can change every game. But I think he can do better. He has played some good games for us but he can do better because he has everything.
"I don't think he has struggled. When I say this, we are talking about a player like Nasri or [Yaya] Toure or [David] Silva, we always think they can change every game they play because they are capable of doing that."
Nasri is set to return to the City team to face Everton on Saturday after missing two games with a calf injury.
Carlos Tevez has been omitted from the starting line-up from the last three matches with Mancini saying the striker is tired and not at the peak of his form.
However, the Italian praised the Argentine for his attitude, saying: "I'm not disappointed about this form recently. About Carlos I can say nothing [critical] because when he plays, even if he is not 100 per cent [on top his game], he's a fighter and he puts everything he can on the pitch.
"But it is clear that we want our strikers to be scoring goals and at this moment Carlos is not strong and for this reason he was on the bench in the last three games. That could change [against Everton] or in the derby. He's not 100 per cent because he has played many games and that is why at the moment he is not so good."