Efficient, controlled and ruthless enough to win without hitting top speed, this was Manchester City proving that Diet Pep has a long way to go before challenging the full-fat version. Chelsea have taken a huge leap of faith with the appointment of Enzo Maresca, who was plotting how to take Leicester City out of the Championship a year ago, but based on their ineffectiveness in defeat against the champions it is going to be a while before Todd Boehly and Clearlake Capital see their occasionally baffling project come together.

The gulf in class and experience was vast. At times, as City made the ball do the work, it was like watching a team of dads outmanoeuvre enthusiastic kids who had only met earlier in the day. In truth, Chelsea were never in it after that inevitable moment when Erling Haaland crept away from Levi Colwill, took a clever flick from Bernardo Silva and set City on their way with the first of what will surely be another prosperous season in front of goal.

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There, in Haaland’s 91st goal in 100 games, it was: a world-class player punishing a team built around the hope of winning tomorrow – although if you wanted one moment to sum up why Guardiola so comprehensively dismissed his former assistant, it could be found in the way City’s second goal arrived six minutes before the end.

First came the loose clearance from Wesley Fofana, one of many centre‑backs deemed more useful than the ostracised Trevoh Chalobah. Then, when the ball dropped to the imperious Mateo Kovacic, the £200m duo of Moisés Caicedo and Enzo Fernández failed to stop the Croatian from powering forward and punishing his old team by bending in a long-range effort that seemed to float through Robert Sánchez.

It was a horrible goal to concede, not least because it was scored by the kind of player who no longer has a space at Chelsea. Maresca has his work cut out managing a bloated squad. He will trust that there will be more fluency once Cole Palmer returns to full sharpness. The Italian will know, though, that he is under pressure to show why Chelsea brought him in after Mauricio Pochettino. City will probably face a sterner examination with a hearing into their alleged breaches of the Premier League’s financial rules reportedly due to begin next month.

Those 115 charges continue to hang over this team and could potentially halt their attempts to win a fifth consecutive title. For now, though, Arsenal and the rest of the chasing pack will be reliant on City dropping their standards. Here, even with Rodri absent, Oscar Bobb out with a fractured leg and Phil Foden, Kyle Walker and John Stones fit enough only for the bench, there was no sign of less hunger from Guardiola’s team.

Maresca, who is from the Guardiola possession school, soon heard the home fans grumbling about his team’s ponderous buildup from the back. Change does not necessarily mean better. Chelsea appeared to be moving in the right direction under Mauricio Pochettino, who led them to sixth place last season, and the mood in the stands was restless. City’s opener was soon followed by plaintive chants for the discarded Conor Gallagher, who is waiting to complete his move to Atlético Madrid.

Gallagher’s energy could have prevented Kovacic from pulling the strings in midfield. Chelsea, though, continue to follow their path. Afterwards Maresca stressed he has too many players. There was a long pause when he was asked if he still wants Raheem Sterling after finding no place for the winger in the matchday squad. Sterling wants “clarity” over his future.

Related: Sense of chaos continues as confused Boehly still searches for Chelsea’s soul | Jonathan Wilson

Maresca, meanwhile, will hold an inquest into the defending that allowed City to take control. It felt too easy when Jérémy Doku dribbled inside from the left flank and found Silva. Caicedo and Roméo Lavia were not close enough to Silva and the Portuguese’s flick unbalanced Chelsea, leaving Haaland to elude Colwill, sort out his feet, hold off Marc Cucurella and lift his shot over Sánchez.

Up and running, City could have been out of sight at half-time. Kevin De Bruyne shot just wide. Silva and Doku tested Sánchez. Savinho, who enjoyed a promising debut after joining from Troyes, went on a few exciting dribbles down the right. As for the hosts, there were a few grumbles after three wayward passes from Fernández, who was controversially wearing the captain’s armband weeks after his involvement in a racism storm that briefly sparked civil war in Maresca’s dressing room.

Chelsea were better with more intensity. There were a few dangerous dribbles down the left from Christopher Nkunku, albeit nothing that unduly worried the excellent Rico Lewis. Nicolas Jackson had a goal disallowed for offside after Ederson failed to hold Palmer’s low shot. Guardiola responded by bringing Foden on for Savinho at half-time. Haaland soon drew another save from Sánchez.

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Maresca needed more in the final third. Pedro Neto came on for his debut, replacing Nkunku, who had done little to show that he was a more effective option than Sterling on the left. Lewis soon had to make a crucial challenge to deny Neto. Ederson denied Jackson.

Yet the pressure soon fizzled out. City trusted Ruben Dias, Manuel Akanki and Josko Gvardiol to hold firm in defence. They had regained control long before Kovacic pounced. Boehly, looking weary, watched his former player score and was soon seen leaving his seat. More than £1bn spent and Chelsea are still playing catchup.