Nasri has had a mixed season for City, but after displaying his quality in recent weeks, Platt has revealed that the Frenchman is highly-rated at the Etihad Stadium.
The former England international told Manchester Evening News: "Samir, since he has been here, has blown hot and cold. When he has been hot he has been absolutely roasting, he has been a tremendous player.
"Every player can have his good games and bad games. Samir is an exceptional player. You don't expect anything different from him.
"Even when people have been critical of him, I don't think he has had bad games. He is a very important player for us."
The former Arsenal player has scored five goals in 34 appearances for City this season.