This could be the summer of great change at Manchester City. Not since Sheikh Mansour became owner in 2008 and began a £1bn-plus investment will there have been as seismic a shake-up as the one being plotted by the hierarchy.

The faltering Premier League title defence and Champions League exit are the catalysts for a forensic examination of strategy before a major overhaul at the Etihad Stadium.

The holistic ethos that recruited Manuel Pellegrini as manager in the summer of 2013 and seeks to harness all parts of the club for common good may remain but at elite level there will be a cold look at what has gone wrong and who is responsible.

Manchester City ready to offload Yaya Touré in clearout and target youth influx Read more

The prime area here is the ageing first-team squad. For a club of City’s ambition to have only Sergio Agüero aged below 27 – he is 26 – of the XI who started the 1-0 defeat to Barcelona at Camp Nou on Wednesday points to mismanagement, so Pellegrini, Ferran Soriano, the chief executive, and the sporting director, Txiki Begiristain, are also under scrutiny.

While Pellegrini’s job is in the balance, Soriano and Begiristain both face appraisals, and will be asked to explain a failed transfer policy since the Chilean became manager. This has featured 11 major signings of which only Martín Demichelis and Fernandinho can be viewed as successes.

Eliaquim Mangala is the headline disappointment, the £42m paid for the defender last summer appearing more exorbitant with each uneven display. Since the close season of 2013 the investment in Mangala plus Jesús Navas (£14.9m), Stevan Jovetic (£22m), Álvaro Negredo (£20m), Fernando (£12m), Bacary Sagna (free), Frank Lampard (free), Willy Caballero (£6m), Bruno Zuculini (£3m) and Mangala has totalled £119.9m. Yet the aim of equipping the first team with two world-class footballers for each position has been a marked failure.

Given the Soriano-Begiristain-Pellegrini axis decide recruitment on a quasi-committee-style basis, who is responsible for each new signing can differ. Although Begiristain has extensive contacts and drives recruitment, he would rarely pursue a player if Pellegrini, as manager, was resistant.

As the pair’s overall boss, Soriano is less hands-on regarding transfers, though he does sign off each deal. City’s failure to meet Uefa’s financial fair play regulations, which limited the club to a £49m net transfer spend this year and a reduced Champions League squad, is down to Soriano, though these restrictions are lifted in the close season.

What is expected, then, is a cull so drastic that by the end of summer a new and unfamiliar City squad may require name badges to identify each other.

The scale of the proposed overhaul means it is easier to name the players City are clear should be retained. Into this band fall Joe Hart, Vincent Kompany, Fernandinho, David Silva, Agüero, Wilfried Bony and Caballero.

Those who are vulnerable form a gang of up to 13, including some of the club’s stellar names. Yaya Touré leads a group that comprises Edin Dzeko, Sagna, Demichelis, Aleksandar Kolarov, Micah Richards, James Milner – his contract expires in the close season – Samir Nasri, Jovetic, Pablo Zabaleta, Navas, Gaël Clichy and Fernando.

The prime assets here are Touré, who has two years left on his contract, and Dzeko, Kolarov and Nasri, who all signed new long-term deals last year. Although not all of this quartet or the other players will be sold, City would hope to raise at least £50m from a fire sale of some, while also reducing the wage bill.

Whoever does depart is expected to be replaced, in the main, by younger players in a bid to inject new life into the squad, with Wolfsburg’s Kevin De Bruyne a prime target and Newcastle United’s Ayoze Pérez also on the radar.

Although the drive to invest in youth is understandable, if the rate of change does prove to be more drastic than a gradual evolution City could endure a difficult season, as whoever is recruited may need longer to settle due to inexperience.

Hart, who was superb against Barça on Wednesday as City were knocked out of the Champions League 3-1 on aggregate, understands the pressure players and management are under to deliver.

Asked about the focus on Pellegrini’s position, the goalkeeper said: “That’s part of being at Manchester City. We all get talked about. I have been the worst keeper in the world recently and Vinny [Kompany] has been the worst defender in the world. We have all had our moment. That’s the role of being at Man City. If we don’t win we are going to get slaughtered.

“We need to show each other and our fans and our people. If people say well done it’s great but proving people wrong has never really been our desire. Our aim is to win things and do well.”

City trail Chelsea by six points in the Premier League having played a match more, and have won only three of their past 12 games in all competitions. “That’s a really bad stat and one I am not proud of,” said Hart. “We are in a really difficult situation at the moment and it’s not one we are going to try to get ourselves out of, we will get ourselves out of it.”

Hart stated the team is determined to finish their last nine league games strongly. “We will make people who have travelled to Barcelona and Russia – where they weren’t even allowed in the stadium [for the Champions League] – think that it was all worthwhile.”

For some players, though, it may already be too late to save their City careers.