After a sequence of unconvincing performances - and results - against Cardiff, Hull and Stoke, City were back to the form of their opening day win over Newcastle as they thrashed United 4-1 at the Etihad Stadium.
Coming against their fiercest rivals and the reigning champions, it was a performance that sent out a loud warning of City's title credentials to the rest of the Premier League.
City played as Pellegrini had promised when he arrived in the summer but after the dip in form that followed the Newcastle display, the Chilean knows the challenge is to maintain such standards.
Pellegrini said: "It is the way we want to play. We played very similar to how we played the first game against Newcastle.
"After that game, for different reasons, (we found) it is not easy to play (like that) with the regularity I want to do it.
"I think that is normal in this period of the season, we are working and playing a different way.
"But the most important thing is the players trust in what we are doing. We demonstrated that during 90 minutes.
"We are just starting. Every match is different but all the fans can be sure we will try to play with the most offensive and attacking team we can.
"Also to be an attacking team you must work on defending and I think we defended really well."
City had a number of stand-out performers on show, from two-goal star Sergio Aguero and Alvaro Negredo up front to captain Vincent Kompany at the back.
Yaya Toure and Fernandinho were rock-solid and dynamic in midfield while full-backs Pablo Zabaleta and Aleksandar Kolarov and wide midfielders Jesus Navas and Samir Nasri did plenty of damage.
Aguero, who opened the scoring after 16 minutes with a superb volley from a Kolarov cross, felt the praise should be shared around.
The Argentina striker said: "The most important thing is that the goals gave us the win.
"I'm very happy that we won three important points, especially against United.
"All the team were brilliant, the defence as well. We're all one team. There are no individual heroes.
"We're all heroes, even the players on the bench. The most important thing is we won and we are happy."
Aguero's opener rewarded City for their high-tempo start, which completely swamped United.
Toure doubled the lead on the stroke of half-time before Aguero and Nasri added two more in the opening five minutes of the second period.
The champions limited damage thereafter and pulled one back with a superb Wayne Rooney free-kick but City had already made their point.
Aguero, 25, said: "We didn't expect it but we were really motivated to win, and that led us to the victory.
"So that motivation helped us play without any anxiety.
"The most important thing is to give all you have, the confidence and the attitude that the team had was very good.
"And in the second half, despite winning 2-0, we kept playing like that. We played very well."
City make a quick return to action as Wigan, their conquerors in last season's FA Cup final, visit in the third round of the Capital One Cup on Tuesday.
Much has changed since the Wembley clash in May with both clubs having changed managers and City having spent more than B£90million on new players while Wigan were relegated to the Championship.
City are likely to make changes with defender Micah Richards, who has missed the start of the season with hamstring trouble, among those who could come in.
Richards did not play in the cup final but sees the latest tie as an opportunity to put its memory firmly in the past.
The 25-year-old told the club's website, www.mcfc.co.uk: "I wasn't involved against Wigan, but there was definitely something lacking.
"Wigan have always played us well and have been a bit of a bogey team, but I would never say the guys weren't up for it because we always want to win, but I just felt they wanted it more on the day.
"That game is in the past now but we have to make sure we put things right in this game and try and progress in the competition."
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- Sergio Aguero