As Manchester United languish in seventh place in the Premier League 14 points behind the leaders Arsenal, it would be wrong to lay all the blame on David Moyes.

Manchester United’s decline started in the summer of 2009 under Sir Alex Ferguson’s watch long before Moyes arrived at Old Trafford.

On May 26, 2009 United reigned supreme as the strongest they had been in their entire history. 

At that moment they were the reigning English, European and world champions, who had just won their third consecutive Premier League title and the next day were due to play in their second consecutive Champions League final against Barcelona in Rome.

A glance at the starting lineup for their triumphant Champions League final a year earlier against Chelsea is a sobering sight for United fans as it shows how far they have declined.

That 2008 lineup shows 11 world-class players at the peak of their powers and on the brink of lifting the Champions League.

The current United side Moyes inherited is a pale shadow of the dominant United sides seen during 2008 and 2009.

The players from those sides have since been sold, retired or been allowed to grow old, and in the vast majority of cases have been replaced with patently inferior players.

In 2009 United boasted the world’s best player in Cristiano Ronaldo, but he was allowed to leave for Real Madrid that summer for a world-record transfer fee of £80 million.

It was assumed United would replace Ronaldo with a world-class talent, but instead they made the short journey to Wigan Athletic to sign Antonio Valencia for £17 million.

Since then Ronaldo has scored 232 goals in Madrid, and during the same period Valencia has contributed just 21 goals to United.

Across the rest of the midfield United could call upon the energy and grit of England’s best player at the 2006 World Cup finals Owen Hargreaves, the goals and flair of Paul Scholes and the composed presence of Michael Carrick.

Compare that with the United’s current stable of midfielders including an older Carrick, Tom Cleverley, Marouane Fellaini, Anderson, Nani and Ashley Young. The gulf in class between 2008-09 and today is vast.

Ferguson inexplicably failed to purchase an established central midfielder in the last six years of his reign and allowed the engine room of his United sides to go in to a steep decline.

During 2008 and 2009 United could boast one of the finest defences in their history with Wes Brown, Rio Ferdinand, Nemanja Vidic and Patrice Evra together forming a formidable barrier.

While Brown has since left for Sunderland, Evra, Ferdinand and Vidic all remain, but their advancing years have taken their toll and it would not be a surprise if all three left the club this summer.

United have tried to inject some more quality and youth in to their defence with the promotions of Rafael, Fabio and Jonny Evans, and the purchases of Phil Jones and Chris Smalling, but they continue to underwhelm when compared to their defensive forefathers.

At the moment the incumbent goalkeeper David de Gea lacks the same authority as Edwin van der Sar, but the Spaniard is a class act and could in time emulate the legendary Dutchman.

It is up front with Wayne Rooney and Robin van Persie where you could argue that today’s side is as strong as the class of 2008 and 2009 when a younger Rooney and Carlos Tevez led the forward line.

It has been impossible to ignore United's decline this season, but it can't be blamed solely on Moyes, and Ferguson must take some responsibility for his failure to properly replace the class of 2008 and 2009.