City suffered for the wrong choice of goalkeeper last season and Guardiola’s hopes will be compromised if Claudio Bravo’s inexperienced replacement does not prove worth the £34.9m outlay

The success of Pep Guardiola’s Manchester City tenure could hinge on a 23-year-old goalkeeper who is untested in English football and has only one full season behind him at a major Portuguese club.

Ederson Santana de Moraes was bought for £34.9m from Benfica this summer. The size of a fee close to the world record for his position indicates two things: how good the Brazilian is believed to be and how keenly Guardiola wishes to remedy his problem at No1.

In last Thursday’s Manchester derby in Houston the Catalan manager got a first glimpse of Ederson in City colours. Guardiola will hope the display is not an augury.

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When Paul Pogba chipped a pass over the top towards Romelu Lukaku the goalkeeper’s classic conundrum of should-I-stay-or-should-I-go was posed. Ederson chose the latter and rushed from his area but failed to take either ball or man. Lukaku carried on, finished from an acute angle and that was 1-0 to Manchester United. Moments later the keeper might also have got a glove to Marcus Rashford’s shot but did not and so a less than satisfactory debut was sealed.

All players make mistakes and a keeper’s are highlighted more because they can be so costly. For Ederson these are also very early days and Guardiola’s hope will be that Thursday night was an aberration that will prove rare.

The unignorable truth, though, is the manager cannot afford another dodgy operator between the posts. This follows an underwhelming first season in charge, of which the bottom-line assessment of Guardiola’s City might be: attack good, back four poor, goalkeeping poorer.

Last season City were knocked out of the EFL Cup after two rounds and reached only the FA Cup semi-finals. They were eliminated from the Champions League at the last-16 stage, two phases earlier than 12 months before. And they failed to mount a serious title challenge, finishing in third place. It meant City won nothing and Guardiola endured a first trophyless year in his gilded managerial career.

To blame all of this on the head coach’s decision over the first-choice keeper is a stretch. But Ederson’s arrival means the 45-year-old moves on to a third No1 keeper in 12 months; when assuming control Guardiola’s first major decision was to bomb out Joe Hart and the England No1 spent 2016-17 on loan at Torino. In his place Guardiola plumped for Claudio Bravo, bought from Barcelona. Here was brave and decisive management from Guardiola. All big calls, though, have an inherent demand they should not backfire and this is precisely what occurred as the Chilean endured a disastrous first season in England.

This is the peril facing Ederson and by proxy Guardiola. If the Brazilian freezes as Bravo did, City can surely not be successful and it will fall directly at the manager’s door.

Bravo boasted a longer and more impressive CV than Ederson when he signed. At 33 he was a professional of 14 years, a decade of these played in La Liga, with Real Sociedad and Barcelona. At the latter he claimed two Spanish titles, two Copa del Reys, one Uefa Super Cup and one Fifa Club World Cup. As an international Bravo won the 2015 Copa América and has won more than 100 caps for Chile.

He was vastly experienced and still he failed. The hint of the troubled season ahead came on debut. Two minutes before the break in last season’s opening Manchester derby, with City cruising at 2-0, Wayne Rooney sent a free-kick into the visitors’ area, Bravo spilled the ball and Zlatan Ibrahimovic scored. Two more errors arrived before half-time and the second should have led to an Ibrahimovic equaliser after Bravo raced out to clear, had a mix-up with Bacary Sagna, and Jesse Lingard squared to the Swede who fluffed the chance.

Facebook Twitter Pinterest Claudio Bravo boasted a longer and more impressive CV than Ederson when he signed for Manchester City but failed to live up to expectation. Photograph: Phil Noble/Reuters

A major reason why Bravo was bought and Hart demoted was because of his supposedly slicker footwork. Yet the second half featured Bravo messing up a dribble inside the area. He showed too much ball to Rooney and Bravo was lucky to avoid conceding a penalty when scrambling to recover. City hung on to win 2-1 but the seeds of doubt over the goalkeeper were sown.

Ederson’s resumé is more modest than Bravo’s but still impressive. In three seasons with Rio Ave, a mid-ranking Portuguese club, he managed 37 Primeira Liga appearances before transferring to Benfica in 2015. He did not make his debut until March 2016, though he did subsequently feature enough to win a championship medal. He became an integral part of a Benfica side that won the Portuguese treble, yet this was his first campaign as a regular starter for one of Portugal’s elite. On departure for City he had made 37 league appearances and accrued Champions League experience.

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If this record plus City’s scouting reports formed the evidence on which Guardiola moved for Ederson, the next question isthis: can he step straight into the Premier League’s spotlight and perform with the instant quality required?

In Houston last week Guardiola said: “Ederson will be for many years a good goalkeeper for Manchester City.” He had similar hopes of Bravo. Now the stakes could not be higher – for City and for Guardiola. With Monaco’s Benjamin Mendy, a left-back, signed as expected, he has joined Kyle Walker, Real Madrid’s utility full-back Danilo and Ederson as new faces for the defensive unit recruited this close season.

The cost of the quartet is around £162m. But the cost to Guardiola if Ederson fails could be far more: his job. It may be harsh but this is why City hired him: to make vital decisions that are subsequently vindicated.

Khaldoon al-Mubarak, the chairman, admitted disappointment at last year’s lack of success while praising Guardiola’s long-term vision for the club. That future is about to start and he will not succeed unless his No1 performs reliably.