The France international has struggled to consistently produce the calibre of performance which earned him a £25m move to City from Arsenal in August 2011.
And City football development executive Vieira says Nasri must learn from a difficult campaign and come back a stronger player next season.
“Samir could do much more,” Vieira told Manchester Evening News. “On a personal level, he is very disappointed with the level he reached this season, for various reasons.
“But he remains an important player in our squad and has learned a lot from this past year. This season has been very important to him and he will be much stronger next year.”
City assistant manager David Platt admits Nasri has been inconsistent throughout the season, fluctuating between “tremendous” performances and abject displays.
But Mancini’s No2 insists Nasri is still a big player for the Eastlands outfit and the former Marseille midfielder still has a future at the Etihad Stadium.
“Since he has been here, Samir has blown hot and cold,” Platt added.
“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, and you don’t expect anything different from him.
“There have been times when people have been critical of him when I don’t think he has had a bad game. He is a very important player for us.”