The France midfielder continued his recent burst of form with an influential and goalscoring display in City's 2-1 semi-final victory over Chelsea at Wembley.
Manager Roberto Mancini joked he could punch the 25-year-old last month after what he felt was a belated display of his true potential.
Nasri's underwhelming performances earlier in the campaign - including an infamous moment when he ducked in a defensive wall against Manchester United - had brought criticism from Mancini.
But there was no mistaking his desire and determination to impress as he troubled Chelsea throughout a gripping semi-final.
Nasri, who hit the opening goal after 35 minutes, told City TV: "I wish I was like this since the start of the season but I had a couple of injuries which stopped me.
"Now I am playing really well, really great. I am full of confidence.
"I try to do my best for the team and we are going to fight until the end for the league and we want to win the FA Cup. It is the right moment."
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