The France international has one goal in 17 appearances for the Citizens in an indifferent campaign for both the playmaker and his club.
But Mancini has been unimpressed with Nasri’s contribution this term, urging the former Marseille star to work harder in training to improve his performances on the pitch.
“I think Samir has fantastic qualities. With his quality, he should always play well. Every game he could be the difference. A player of this quality could be one of the best players in Europe. But it’s not happening.
“Sometimes a player thinks it’s enough what they did the year before and doesn’t understand that every day they should improve.
“If you are a top player you know you can improve until the last day of your career but sometimes you get players who think it is not important to work and this is their worst mistake.
“Samir can do better than this year. He is a top player but he has not been playing at his level.”