City suffered a 2-1 defeat at Napoli on Tuesday after two goals from Edinson Cavani.
City will now hope that Villarreal manages to beat Napoli in two weeks’ time. City will also need to defeat Bayern Munich at the Etihad Stadium in order for the Premier League side to reach the knockout stages.
Mancini told Sky Sports: “We have another game and Villarreal can beat Napoli.
“It is the first time we have played Champions League but I don’t think Villarreal will lose another game, they can win or draw – why not?
“Everything is not finished – never say never.”
Mancini added: “We didn’t deserve to lose this game, we should think we can score three or four goals every game. We wanted this because that is our mentality.
“After our equaliser, we had two more chances to go 2-1 up, it is strange that we conceded this goal after 10 minutes.
“We had other chances to score, their goalkeeper was fantastic and saved three or four chances. But if you lose, probably you made mistakes.
“We conceded two stupid goals, we know Cavani goes on the first post. Cavani is a good player, a good striker, he scores goals and works for the team.”
