The Italian manager believes the confidence and momentum gained from Wednesday's 3-0 victory over the Spaniards can help his side progress in the competition later this month
Two goals from Yaya Toure and a penalty from Mario Balotelli gave the Citizens a two-point advantage over the Italian outfit in Group A ahead of the showdown on November 22.
“I think this win is important because now we have a good chance,” Mancini told the press after the game.
“We know that everything will be in Naples.
“I think it will be an incredible atmosphere. There will be 70,000 people at the stadium.
“I think it is very difficult to play but it is important to go there with this result.
“I don't think it was easy to win here but we played very well and after the first goal it was easier. That was really important.”
Villarreal were missing several of their key players due to injury but Mancini was nevertheless satisfied with the way his team controlled a potentially hazardous encounter.
“Villarreal were missing four or five important players but it is always difficult to win away in the Champions League,” the Italian continued.
“We had 65 per cent of ball possession, we scored three goals. I think this was important for our confidence.
“I think we have improved, not just in the Champions League.
“It is important for us to go in the second stage, then everything can happen with us because we are a good team. We can improve a lot in the next month.”
Some fans were concerned when in-form Spanish star David Silva was substituted while clutching his back in the second half, but the City manager played down the situation.
“I don't think this is serious. He took a knock on his back,” said the 46-year-old.
“Also we play again in 60 hours against QPR. I think he can recover well.”