City tackle Napoli in Champions League Group A at the San Paolo stadium here on Tuesday knowing that a victory would see them into the knock-out rounds.
And although Napoli coach Walter Mazzarri claimed the English Premier League leaders are almost as good as the imperious Spanish pair, his City counterpart doesn't agree.
"We have great players like Sergio (Aguero), Mario (Balotelli), Edin (Dzeko) and (David) Silva but it's too soon to say we're close to Real Madrid and Barcelona," said Mancini.
"We've only been building this team for a year-and-a-half and we've been going too fast.
"We have got to improve a lot, it's not easy to play in two different competitions.
"We're closer to Napoli than we are to Real or Barcelona. Napoli have a great team and a great coach and that's why it will be difficult.
"Like Mazzarri said, we'll try to do our best but we've still got a lot of work to do to reach the level of those teams."
City are two points ahead of Napoli in the group and face leaders Bayern Munich at home in the final group game while Napoli will travel to Villarreal.
But despite their more favourable position, Mancini says there is no chance his side will play for a draw.
"It's not in our mentality to not play the game (to win) so it doesn't matter that we can also afford a draw.
"We'll try to force the game knowing that Napoli are a good team who can put us in trouble.
"But like Napoli we're also improving and we have to continue on our path."
However, the Italian is expecting Napoli to have a real go as even a draw would leave them needing to win their final group game in Spain to have any chance of progressing.
"Right now we're in good form but every game is difficult and we're playing twice a week," said Mancini.
"This is very hard and tomorrow is so different from other games, it's the last chance for Napoli so tomorrow will be a very tough game for us."
The former Fiorentina, Lazio and Inter Milan coach was also keen to play down worries that there will be trouble between the two clubs' fans.
Last season several Liverpool supporters were stabbed the night before their Europa League game against the Italians while a couple of Bayern Munich fans were stabbed here last month.
"Those who asked me I told them go, there's no problems, it's a lovely city to visit," said Mancini.
"I don't think fans won't come because of (what happened before), they will be able to see a great match and a lovely city.
"(Fan violence) can happen in every stadium and every city, everywhere.
"For us the important thing is that we can do our job but I don't think something will happpen around the stadium."
For City striker 'Kun' Aguero it is a first visit to a stadium that was graced by his illustrious father-in-law, Diego Maradona.
But that doesn't faze the Argentine.
"I'm definitely not nervous, I will have fun. I know Maradona did great things here in the past but I'll be calm and try to enjoy it," he said.
"I don't think I'll have any problems from the fans, I never have had in any ground and I think the fact Diego played here will help me.
"In the past I spoke with him about Napoli but I didn't need to because I'd seen them on television.
"He's a God for Napoli just as he is in Argentina and I'm happy about how he's seen here because he's Argentine."
Lives text commentary from tonight's Champions League fixture:
Source: AFP
Source: AFP