Manchester City have risen to elite status in European football under Pep Guardiola as they have invested heavily to give their manager a playing squad capable of winning every trophy.
City spent just shy of £200m in transfer fees in their first season under Guardiola, with John Stones, Leroy Sane, Ilkay Gundogan, Gabriel Jesus, Nolito and Claudio Bravo among the arrivals at the Etihad.
The following year, City broke the record for spending in a single transfer window as their defence was overhauled.
Aymeric Laporte, Benjamin Mendy, Kyle Walker, Danilo and goalkeeper Ederson were among the arrivals, while attacking midfielder Bernardo Silva was also recruited.
By this stage, Guardiola had assembled a squad which not only allowed City to win successive Premier League titles but also to break multiple records along the way.
In the two summer windows since, only Riyad Mahrez and Rodri have arrived as instant first-team players, but this year City might need a host of top-class arrivals.
This is not because Guardiola’s side are a whopping 23 points off the title pace following nine league defeats this season, it is just an eye into the mini-overhaul needed at the club.
It is the first time in his managerial career where the Catalan has truly needed to begin the rebuild of a side. At Barcelona the core of his eventual starting XI were already in place, while it was a similar story at Bayern Munich and City.
Kevin de Bruyne and Raheem Sterling had arrived at the Etihad a year before Guardiola, while dressing room stalwarts such as David Silva, Vincent Kompany, Sergio Aguero and Fernandinho have all been central to their successes in recent years.
Yet City did not replace the loss of Kompany last year and, coupled with injury problems for star defender Laporte, they have been left badly short at the heart of their defence.
There are long-term doubts over the futures of Stones and Nicolas Otamendi, while Eric Garcia has only played a handful of games and is also wanted by Barcelona.
An exclusive story by Catalan outlet Diario Sport claimed Barca were already negotiating for the return of the defender this summer.
But even if the impressive Garcia remains, City need to strengthen at the back. Fernandinho has provided emergency cover this term, but he is now 35. Next summer, he will be out of contract and is likely to leave.
There is a similar, if slightly less pressing issue with Aguero, who remains the club’s primary attacking talent. The Argentinian striker celebrated his 32nd birthday this month and is beginning to miss significant parts of the season through injury.
Jesus is the only other recognised striker in the squad, and while the Brazilian has many qualities, the loss of Aguero is always felt and another striking option is necessary.
Of course, all this comes in the same summer that two established City attacking stars have confirmed their departures. David Silva’s wonderful decade at the club is coming to an end and Leroy Sane has confirmed his switch to Bayern Munich.
While the emergence of Phil Foden as a bona-fide first-team player is welcomed, it is likely the club will need to sign another creative player to cover the losses.
So a significant part of the spine of Guardiola’s team will need replacing, while a new back-up goalkeeper for Ederson could be needed with both Claudio Bravo and Scott Carson out of contract this summer.
If all this was not enough to worry about, there is likely to be at least one full-back signed this summer. Joao Cancelo has not dislodged Walker at right-back, and the Portugal international is said to want a move away to guarantee first-team football.
Earlier this year, The Telegraph claimed City could pull off a swap deal with Barcelona for Cancelo, with Nelson Semedo going in the opposite direction.
Whilst that deal is unlikely, there is a chance Cancelo will be sold and replaced, while at left-back only Oleksandr Zinchenko - a natural attacking midfielder - is available to cover Mendy, who has had sporadic form and fitness issues across his spell in Manchester.
The significance of full-backs to Guardiola’s team is obvious. These are key positions for his City, so it is likely he will be eyeing potential improvements in each position this summer.
This is the first time in Guardiola’s coaching career where multiple positions in his squad have needed instant improvement, and he is also unfamiliar with his side being so far from league-winning level.
Sunday’s defeat at Southampton was the latest in a long line of matches in which City played well and to the Catalan’s instructions - controlling possession and creating multiple scoring opportunities - but ultimately lost.
There is a fear that rival coaches in the Premier League have found a way to combat and limit the brilliance of Guardiola’s City, certainly with this current group of players.
The level of new champions Liverpool, and potential improvement of Chelsea and Manchester United, means there is no room for error. City need to get this pivotal transfer window right.