The end of an era has already begun at Manchester City. The evidence is staring us in the face. When the greatest teams start to fade, reality is always delayed by a desperation to prove that the past is a pointer to the future. That's the space now being occupied by Pep Guardiola and his players.

It's a trap that every team falls into eventually. Manchester United clung to the belief that the standards set during Sir Alex Ferguson's two decades of success would ensure a swift return to glory following his retirement in 2013. But, more than 10 years later, United are now among the also-rans.

Liverpool experienced their own painful demise in the 1990s for similar reasons. Having been so successful for so long -- four European Cups in the space of seven years and 11 league titles in 18 years -- they assumed that previous success would return because that's what had always happened. But it took them 30 years to win a title after their success in 1990.

As City lost 2-0 at Liverpool on Sunday -- suffering a sixth defeat in seven matches and losing four consecutive Premier League games for the first time since 2008 -- the fault lines that eventually brought down the empires at United and Liverpool were there in plain sight. At Anfield, City were unrecognisable from the side that won six league titles in the last seven years and won the Champions League 18 months ago.

City's problems were embodied by players such as İlkay Gündoğan, Nathan Aké, Kyle Walker and even Kevin De Bruyne. And, for differing reasons, Matheus Nunes and Manuel Akanji. Ageing players and poor recruitment are the most debilitating combination for any club, and those that win tend to do so because they blend the energy of players at the peak of their powers and young stars making their way in the game. They also know when to move players on and when to recruit the next big thing.

Liverpool allowed their great team of the 1980s to grow old and made mistakes when signing inferior players to replace them. The same happened at United: Chris Smalling and Phil Jones were signed as long-term replacements for Rio Ferdinand and Nemanja Vidić, Luke Shaw to replace Patrice Evra and a 31-year-old Bastian Schweinsteiger to run the midfield having already played out his best years at Bayern Munich.

It is a gradual process of diminishing standards, but suddenly, the consequences of that hit home. City are now paying the price for repeating the same mistakes that played a significant role in the collapse of United's and Liverpool's dynasties.

City's off-field problems -- the club are fighting 115 charges of breaching the Premier League's financial regulations -- have undoubtedly contributed to their mistakes in the transfer market. Deals have been done that are unlikely to have been signed off had they not been attempting do business with the cloud of doubt hanging over the club.

The decision to re-sign Gündoğan from Barcelona this summer was out of character for City, but despite the former Germany international approaching his 34th birthday at the time, they signed him nonetheless. But after a year away in LaLiga, Gündoğan has returned to the Premier League looking like a player who cannot cope with its pace or intensity.

Had Ballon d'Or winner Rodri not sustained a season-ending cruciate ligament injury in September, Gündoğan may have only been a bit-part player in his second spell at the club. But with Nunes yet to impress in a City shirt since his 50 million arrival from Wolverhampton Wanderers 18 months ago, Gundogan has made 18 appearances in all competitions since returning to the Etihad.

Gündoğan and Nunes playing together in midfield at Anfield highlighted how City are suddenly suffering from recruiting inferior players to those who have gone before them. It's the drip-drip effect that leads to decline. Where are the long-term replacements for Walker (34) or De Bruyne (33)? City know that both, who have been integral to their success under Guardiola, are not the players they once were and becoming susceptible to injury, but they have not yet identified players capable of succeeding them.

City are now having to play catch-up, and that increases the risk of making a mistake. If they get it wrong, as United did with Smalling and Jones, it becomes increasingly difficult to get back on track. And by allowing young talent including Cole Palmer (Chelsea), Julián Álvarez (Atletico Madrid), Taylor Harwood-Bellis (Southampton) and Liam Delap (Ipswich Town) to leave over the last 18 months, City have offloaded players who could have helped ensure a smoother transition between the winning teams of the past and a successful new era. Raheem Sterling, Gabriel Jesus, Aymeric Laporte and Riyad Mahrez have also left City in the past two years, though to limited success elsewhere.

The laser-like focus that saw City sign the best players -- their treble-winning squad from 2022-23 was full of players who were signed young and developed by Guardiola -- has gone and they have started to make too many mistakes and misjudgements. They have taken their eye off the ball, the team has suddenly grown old in key areas and opponents no longer fear them as they did. That's why Bournemouth, Brighton & Hove Albion, Tottenham Hotspur and Feyenoord have beaten or drawn against Guardiola's side on this recent winless run. What happened at Anfield was all of City's shortcomings combining at the same time while, in contrast, Liverpool looked hungry, vibrant and energetic.

City will still win big games this season and may yet even win a trophy, but their decline has already started. It feels like it has happened in the blink of an eye, but it always does, until you realise the evidence has been there all along.