Despite a £226m summer transfer splurge, Manchester City are still vulnerable in central defence as Pep Guardiola’s team welcome Liverpool for the early kick‑off on Saturday. Premier League hostilities resume at the Etihad Stadium after the international break against a Jürgen Klopp swarm‑and‑attack unit that should offer a gauge of how City’s failure to strengthen at centre-back may affect their season.

Vincent Kompany, John Stones and Nicolás Otamendi are the manager’s leading players in the position. With Guardiola now preferring to utilise a three‑man defence and wing-backs, injury or loss of form for one of those will leave a hole as the only deputies at centre‑back are the unfancied Eliaquim Mangala and the inexperienced Tosin Adarabioyo.

In fact, three matches into the campaign and that scenario has already occurred. Stones was hauled off in the second half of the 1-1 draw with Everton and dropped for the 2-1 win at Bournemouth, City’s last outing before the break, when Guardiola opted for a back four.

Liverpool usually line up in a 4-3-3 that features the pace of Sadio Mané and Mohamed Salah sandwiching the false No9 Roberto Firmino. Behind this trident Emre Can, Jordan Henderson and Georginio Wijnaldum protect the defence and pull the strings. Under Klopp this forward six will be urged to press City for the full 90 minutes.

Guardiola has an unbending faith in possession. The 46-year-old’s view is clear: if City ball-hog against Liverpool, the red shirts will be moved about, space will widen and his side will win.

Yet the Guardiola strategy failed enough times in 2016-17 for City’s title challenge to fade away by the end of November and they trailed in third, a yawning 15 points behind the champions Chelsea. Keep‑ball‑permanently may be shorthand for the Catalan’s ethos yet when this fell down at crucial moments his defence failed to function.

It moved Guardiola to pay £158.2m of the £226m spend on bolstering his rearguard. Three new full-backs – Kyle Walker, Danilo and Benjamin Mendy – arrived, plus a goalkeeper, Ederson. Yet by 1 September the manager was actually a central defender lighter because Jason Denayer had left for Galatasaray.

Guardiola began the close season wanting the Southampton centre-back Virgil van Dijk but Txiki Begiristain, the sporting director, and the chief executive, Ferran Soriano, baulked at the £60m starting price and moved next to West Bromwich Albion’s Jonny Evans.

Again, the Northern Irishman failed to arrive. The reason offered was that City could not free up a space by shifting Mangala, despite Crystal Palace and West Brom wanting him. All of this highlights Guardiola paper-thin centre‑back resources and his view of Kompany, Stones, Otamendi, Mangala and Adarabioyo.

Kompany is enjoying his longest run of consecutive outings – 11 – for three years yet concerns remain about the captain’s robustness. The spectre of a fragile physique continues to lurk over the 31-year-old’s availability. He is understood to be a doubt for Saturday because of a calf injury sustained on international duty.

Stones is the player Guardiola was desperate to sign before he took over in summer 2016. Guardiola wanted the Yorkshireman for his perceived technical ability and penchant for initiating play from the back as a kind of quasi‑midfielder. Stones, though, is now in danger of becoming a mere squad player. The 23-year-old was in and out of the XI last season and there are no assurances he will be in the team to face Liverpool.

Otamendi has begun all three matches yet needs Kompany alongside to help ease the errors that can pock the Argentinian’s game. He also has an unfortunate habit of going to ground too soon.

While Mangala came close to departing, Adarabioyo may well be a confused 19‑year‑old. After nearly leaving in the close season, he agreed fresh terms that tie him to City until 2021. Yet his stock is so low that Adarabioyo is yet to make a match‑day squad, and Mangala is ahead of him.

The hope for Guardiola is that this term does not become a repeat of the last, when he bewailed how City would “arrive” in an opponent’s danger area but fail to score. He would often point to how, conversely, the same opposition required only one chance to score against City.

Wayne Rooney celebrates putting Everton ahead at Manchester City, to the consternation of Vincent Kompany, left, and John Stones. Photograph: Tony McArdle - Everton FC/Everton FC via Getty Images

In this sense the Everton game was an unwanted carbon of the pattern. Ronald Koeman’s side were dominated throughout yet led for half the match and escaped with a point.

Afterwards Guardiola admitted he fears City will once more fail to find a killer touch when required and said: “They [Everton] had one on the target. They scored a goal.”

This is a damning analysis of City’s defensive fragility from the man who leads them. Guardiola is correct: in virtually the only time Everton got at the home side, Dominic Calvert-Lewin roved down the right and Wayne Rooney drove at City in a central defensive area to score.

That contest was on 21 August, more than a week before the transfer window closed. The manner of the strike further crystallised the need to buy (at least) one high-quality centre-back. This did not happen and so raises a simple question: why?

The hope for City is that against Liverpool a convincing answer will be provided. If not, the Guardiola-Begiristain-Soriano summer recruitment drive will be scrutinised further.

Top of this agenda would be why, after a near quarter-billion-pound investment, does City’s central defence remain as weak as last season?