All talk has now turned to who will replace the 71-year-old as manager of the storied club. The leading candidate for the job seems to be current Everton manager David Moyes, whose contract is up at the end of this season.
What makes Moyes the perfect replacement for Ferguson? Very little. It's easier to say why he isn't the right man for the job.
Moyes joined Everton in 2002 and has been with the club ever since. That's commendable, especially since so many clubs hire and fire managers as if it's going out of style. Moyes being the manager for one club in the Premier League for 11 straight years is a plus.
United will want a manager who will stay for the long haul. Moyes can be that man.
However, Manchester United is not just an average club. It is one of the biggest football clubs in the world and has million upon millions of fans worldwide.
No offense to Everton, but the team is not on the same level as United. The following isn't as massive, and the expectations are not as high.
No average manager can just come in and take over the helm at Old Trafford. It is sure to be overwhelming.
Moyes is not prepared for this challenge and has not been groomed for it at Goodison Park.
For example, the Everton talent is not nearly as supreme as the United talent. Moyes does not have to deal with superstars and their egos the way that Ferguson has had to.
There will be high-profile players competing for only 11 spots on the field. Will Moyes know how to please them all? Does he know how to deal with the backlash? Most likely not.
While Everton has good players, it's difficult to classify any as superstar talent. Their egos simply are not as big as players who are on the high-profile clubs.
Simply put, Everton players are most likely easier to deal with than United players.
Speaking of Goodison Park, it holds exactly 40,221 fans. Old Trafford holds almost twice as much at nearly 76,000 fans. The stage is much bigger in Manchester, Mr. Moyes. Be sure you know what you're getting yourself into.
More fans means more people to love you. However, it can also mean the exact opposite.
If Moyes doesn't deliver, he will hear it from all 76,000 in OT and the millions more around the world. Expectations are higher and people are far more critical.
But truth be told, the Scot has been solid at Everton. The Toffees have little money to play around with, yet the team has finished in the top half of the table for most of his tenure. This season will most likely see them finish ahead of bitter rival Liverpool.
Not bad, but this does not mean he is a good fit for United. Top-half finishes are not what United aims for. The goal for every season is to win. Win the Premier League. Win the UEFA Champions League. Win the FA Cup. These are not the goals he will be accustomed to.
Ferguson has brought numerous trophies to Old Trafford over his 26-year reign. There is not one major European trophy that he hasn't won. Moyes has not won Everton one trophy. Not one. Yet he should replace Ferguson?
Season after season, Manchester United takes on the best of Europe in the Champions League. Moyes has little experience with European football. How can the team compete with a manager who is not successful in arguably the most important tournament to any team?
Domestically, United should be okay with Moyes, but success is up in the air on the European stage. He hasn't proven that he can lead a team in the Champions League past the qualifying rounds. This will not be good enough.
Sure, he is a good manager, but he lacks the panache to be Manchester United's new manager.
No one knew Ferguson would become the legend that he is today, but United wasn't the same club back then. It was fine to bring in someone out of the ordinary and give him the reins. But those days are over.
Because of Sir Alex Ferguson, Manchester United is a bigger and more successful club. It cannot have just anyone in charge.
It needs a bigger name, a name synonymous with success.
David Moyes is not that name.