"Any successor to our current manager may not be as successful as our current manager," United said in the risk factors section of official documents that accompanied the $2.3 billion listing.
This theory will now be tested after 71-year-old Ferguson, the combative Scotsman who has become the most successful manager in the history of English football, said he was retiring this month after 26 years in charge of the team.
United shares fell 3.5 per cent to $18.10 in early trade in New York, having climbed in recent months from last August's $14 launch price.
"Manchester United has been transformed as a football club under the management of Sir Alex Ferguson," said Dan Jones, a partner in the Sports Business Group at Deloitte.
"Financially, the last 26 years have coincided with a wider revolution in English football with massive investment in the game and the growth of the Premier League, particularly driven by domestic and international broadcast deals," he added.
United, controlled by the American Glazer family, gave no word on who will step into Ferguson's shoes. David Moyes, a quietly spoken yet forceful Scotsman who has turned Everton into a Premier League force on limited resources, was the leading contender, according to bookmakers.
Players such as David Beckham and Cristiano Ronaldo have come and gone but Ferguson has been a constant presence on the touchline at Old Trafford for more than a quarter of a century, urging on his players and raging at perceived injustices.
With Chief Executive David Gill also stepping down this summer, it's suddenly all change at the club. Executive vice-chairman Ed Woodward will take over many of Gill's duties and work with the new manager on player signings.
The club is in the process of discussing a new agreement with long-term kit supplier Nike to replace a deal worth upwards of £25 million per season.
"We believe that Manchester United is a first class institution with a 135-year history of excellence that has wisely been planning and preparing for the eventual retirement of Sir Alex Ferguson," stock market analyst Randal J. Konik of Jefferies said in a note.
Although the club's financial future is sound, the new manager will face pressure to deliver trophies rapidly.
United's growth as a business since the 1990s has coincided with a huge surge in interest in the Premier League at home and abroad. English football got itself luc
