Sergio Agüero has two nuggets of good news for Manchester City supporters in this trying week of Bayern Munich's humiliation of their team. The striker says that he never contemplates leaving the club and he believes Wednesday evening's 3-1 defeat by the Champions League holders may prove a pivotal moment in City's quest to conquer the continental elite.

Agüero is in relaxed mood the day after the night before at a rainy Carrington, the club's training centre. Of the emphatic lesson handed to the 25-year-old and his team-mates by Arjen Robben, Franck Ribéry, Philipp Lahm and company at the Etihad Stadium, Agüero says: "Clearly it was a bad day. We knew Bayern were a fantastic team and they proved it. But today is a different day and we have to carry on and keep going. It's just something that happens in football."

This is only City's third Champions League foray so there is no shame in taking a beating from a Bayern team who appear an even stronger, slicker and faster juggernaut because of the influence of their new coach, Pep Guardiola.

So, could the ordeal be important for City's fortunes in the competition? "Yes. It could be," says Agüero. "It could be an experience for us to learn and perhaps we can work on that and help us for the next time we find ourselves against another fantastic team like Bayern."

Joe Hart again drew scrutiny for the mistakes that allowed Ribéry's opener and Robben's second-half strike, both of which beat him from distance. But after a smiling Hart was seen leaving Carrington, Agüero is certain about the goalkeeper's status at the club. "Joe Hart is one of the best goalkeepers in the world, we all know that," he says. "We can all have good and bad days. But he will, without a shadow of a doubt, come out bouncing and prove what a great goalkeeper he is."

When Agüero looks around that City changing room he sees Yaya Touré, who has tasted Champions League glory with Barcelona, and David Silva, a World Cup and European Championship winner. Players such as these give the Argentinian confidence that Manuel Pellegrini's side can grow into the competition. "Yes. The club has done things the right way in the last four or five years," he says. "Not only the players who are here now, but the fantastic players that have been in the club. Now we have a new manager with a new challenge, we need time to implement his ideas. But the club is doing the right thing, it's doing it properly. We're all fighting for the same, which is to make the club the best possible."

He is clear about what City can achieve. "We will try to always do the best whether it is the Premier League, the Champions League, a cup game. We always want to win and we always want to do the best for Manchester City and the fans."

Champions two seasons ago, Agüero believes they can win the Premier League again. "We are improving every year. The club is growing, we are working in the same direction to get as high as possible. Some years are better than others. But it's a much better club, a much better team than it was four or five years ago. So we just have to go in the same way."

Agüero ranks as the nonpareil hero of the City congregation. His five goals in six derby appearances against Manchester United and the last-gasp strike of the 2011-12 season which claimed the title ensure this status. Of sparkling against United, he says: "Yes, I really enjoy derby games anyway and things have gone my way against Manchester United. But it's not only important for me, it's important for the club, it's important for the fans and hopefully I will keep scoring goals in every [derby] game."

He joined City in summer 2011 and is contracted until 2017, with no plans to leave. "I'm very happy at City, very happy since the day I came. I knew that the project was good and in my head there is nothing else but Manchester City, so how long I'm going to be at City is just never a question.

"I'm happy here, my family's here when they come to England, all I can do is give everything I have for the club and concentrate on achieving for the club."

This loyalty to City is shared by his son, Benjamin, whose mother, Giannina, is Diego Maradona's daughter. With Agüero now divorced from Giannina, Benjamin lives abroad but is still a City supporter. "Yes. And he's very aware, when I go away from him he doesn't say: 'You are going to Manchester'. He says: 'Oh you're going to City'. And, he goes to school and is always wearing the Manchester City top, so he's a big fan."

A YouTube clip of Benjamin aged 18 months suggests he already has his father's rocket of a right foot. With arguably the world's best ever player for a grandad, could Benjamin turn out to be better than either Maradona or Agüero? "If it is true that it comes from the genes, then he will be quite a good player," he says. "But let's see what will happen because he enjoys roller skating and playing hockey."

The closeness Agüero enjoys with his family is illustrated by his own dad being present during our conversation. Leonel was also a footballer, playing for the reserve team of San Martín de Tucumán, a third division club. He discusses his father's career with a smile: "My memories [are] of when he was already 32, 33, and I remember seeing that he was clearly a quality player. From what they have told me of him from before, which I don't remember, he was gifted."

Agüero, who took Leonel's mother's maiden name, grew up on the outskirts of Buenos Aires, moving near Los Eucaliptus, a shantytown, aged three. By then he had acquired the "Kun" moniker, which is on his City shirt. It derives from a Japanese cartoon, Wanpaku Amukashi Kum Kum, which Agüero enjoyed as a toddler. "Yes I made the name mine with the N," he says. "I don't remember watching it but my family tell me that I used to all the time."

Only 35 days after his 15th birthday he would eclipse Maradona by becoming the youngest player in the Primera División when making his debut for Independiente. He says: "At the time it really didn't click, everything happened really quickly, I trained for four days with the first team and there I was playing. So I didn't take it in really. It was something normal at the time, I had to play and that's it. When the time has passed, now I look back and yes, it is a huge achievement."

Goals – 175 of them – in all competitions have followed for Independiente, Atlético Madrid, who he joined for an Argentinian record €23m (£19.5m) at 17 in August 2006, and City, who paid £38m two years ago.

Can Agüero remember the first ever goal? "Yes. It was against Estudiantes de La Plata, I was 16," he says. "I received the ball on the edge of the area, controlled with the left and moved to the right-hand side and just hit it hard and it went on the left side of the goalkeeper."

How does football here compare to his homeland? "It's completely different in Argentina to the Premier League. Here the supporters are closer to the pitch, which is something I really enjoy," Agüero says. "I enjoy having that atmosphere. Having said that, in Argentina the fans are louder, they support always for 90 minutes, the atmosphere is fantastic. But in my opinion I am in the best league in the world. So I'm very happy with the way things are in England, the fans are fully supportive. I'm delighted to be here."

In Agüero's first Premier League campaign he scored 23 times, including that strike against Queens Park Rangers, which sealed City a first title in 44 years. He plays down his part in the Premier League's most famous moment.

"That is something that is on your mind because it is an important goal but it is a different season, a different championship. It's something that is just a memory. The idea is just to keep going and trying to score as many as possible."

Yet every day someone wants to talk about it. "It does happen every time with fans, not only in England also in Argentina. But it is normal." Unlike Agüero, who is hardly the ordinary footballer.