After winning three Premier League titles in a row from 1999-2001 they endured a difficult season in 2001-02, finishing third, and needed to recruit the best defender in the country to steady the ship.
Ferdinand, who 12 years on has announced he is leaving Old Trafford at the age of 35, fitted the bill perfectly.
The tall and elegant centre back had made his name at West Ham United from 1996-2000 before moving to Leeds United for £18 million and becoming a cornerstone of the team which reached the Champions League semi-finals in 2001.
But as Leeds imploded with financial problems, United made their move to staunch the defensive instability which undermined the 2002 season and made Ferdinand the then most expensive player in British football history at £29.1 million.
United manager Alex Ferguson wanted a linchpin for the next 10 years and Ferdinand duly obliged.
It all started smoothly as United won the title in Ferdinand's first season at the club but then there was a major hiccup.
Ferdinand missed a mandatory drugs test in 2003 and was banned for the rest of a season in which Arsenal's Invincibles won the title with an unbeaten record.
Restored to the staring line-up, Ferdinand began to show his true worth but Chelsea coached by Jose Mourinho proved an irresistible force and won the Premier League in 2005 and 2006.
In 2006, however, United moved to provide Ferdinand with a significant defensive partner by signing Serbian Nemanja Vidic from Spartak Moscow and it was a match made in heaven.
The muscular and feisty Vidic, who is also now leaving United after the club's tortuous season, was perfectly complemented by Ferdinand's more subtle defensive skills.
The pair blended superbly to provide Ferguson with the bedrock he wanted and three Premier League titles went to Old Trafford from 2007-09.
The 2008 Champions League final was the pinnacle of Ferdinand's career and further Premier League titles followed in 2011 and 2013.
Hampered by injuries in his later years, Ferdinand proved less of an dominating influence than he would have liked but when he played there was always a sense of calmness in the United rearguard.
After guiding United to the 2013 Premier League title in his final season in charge of the club, Ferguson paid the ultimate tribute to his defensive rock who also played 81 times for England.
"Rio Ferdinand has had his best season at the club," Ferguson said.
"We have had continual problems with the centre-backs being fit. Although we have left him out of certain games because we have managed him the right way, at the most important times he has been there."
That was Ferdinand. There when Manchester United needed him most in 12 magnificent years at Old Trafford.
Piece courtesy of Reuters
- Sports & Recreation
- Rio Ferdinand
- Premier League
- Manchester United
- West Ham United
- Leeds United