Nasri was in fine form last weekend as City recorded a comfortable 4-0 win over Newcastle United in the Premier League.
The Frenchman has been disappointing for large parts of this season and Mancini has admitted that he is frustrated by Nasri's performances for much of the campaign.
He told the Daily Mail: "I would like to give him a punch. Because a player like him should play like today always. Always. Every game. Maybe one game sometimes he can play badly but with his quality that is all.
"I don't know what the difference was today. I can't understand sometimes a player with his quality doesn't play like today every game. I think that the second year is always difficult to win again. And sometimes a player can think it is enough to play 50%t. Probably we had this problem this year.
"I don't know if Samir agrees but I think that every player is intelligent and is clever to understand his performance. I think that today he knows that he played very well."
The 25-year-old has scored three times in 29 appearances for City this season.