Roberto Mancini said last night that it was still possible for Manchester City to finish top of Group A after Sergio Aguero's dramatic late goal gave the club their first win in the Champions League against Villarreal.

The City manager, whose team won 2-1, said that the group was open after Napoli drew 1-1 with leaders Bayern Munich in Germany last night. City play Villarreal in Spain in two weeks' time, a game they must win before they go to Naples on 22 November for a crucial match against the Italians.

Mancini said: "I hope the win will be very important. It was important to win our first game in the Champions League and I think anything can happen in this group in terms of first place. We go to Villarreal in 15 days and it will be very important because they are a good team and play football very well.

"Yes, 100 per cent [the Napoli game is the decisive one]. I think that game will be very important. Before this we will play the game in Villarreal but the game in Naples will be the crucial game. First place is open in the group."

The club denied there had been a fight between Aguero and Villarreal players in the tunnel after the match. Aguero later tweeted that he had not "mocked" any of his opponents after the match.

Having reacted to Aguero's winner with an uncharacteristically demonstrative celebration, Mancini said that his team had missed too many chances. "When you have one chance you must score because if you don't the game can go the other way," he said. "We deserved to win this game. Villarreal played on the counter-attack and anything can happen, one goal could finish the game, so because of this it is important to score and take your chances.

"Playing in the Premier League takes a lot of strength and energy and after three days to play in Champions League is very hard. Last year we wanted this, to play in the Champions League and improve as a team. Every team that has played in the Champions League for years doesn't have this problem. The the first year is hard but we want to do it and stay on this stage."

One of the game's turning points, just before City equalised through an own goal by Carlos Marchena, came when Mancini substituted Adam Johnson with five minutes of the first half remaining. The England international looked furious as he came off but Mancini said it was necessary to alter the shape of his team.

He said: "We were conceding four or five counter-attacks and didn't have many players in the middle. I wanted to move Yaya [Touré] behind Edin [Dzeko]. Adam played very well but at it was a tactical substitution.

"I spoke with him and he understood. Sometimes every manager can decide if the team needs a tactical sub and unfortunately players have to leave the pitch and will be disappointed, but Adam is a very important player for us."

City are expected to announce either today or tomorrow what the nature of their charges are against Carlos Tevez for his actions during the previous Champions League game against Bayern Munich. Mancini refused to discuss the situation last night, Ahead of the derby with Manchester United on Sunday, he said the win last night was important. "It's good for our confidence and important to go there and do well because it will be very hard."