Manchester United manager Sir Alex Ferguson has announced he will retire after 26 years. (David Cannon/Allsport)

In his 26 years as the manager of England's Manchester United board, Sir Alex Ferguson helped the club win 13 Premiership League titles, two European Champions League titles and five Football Association Cups.

If you're not familiar with soccer jargon, then just compare it to John Madden or Vince Lombardi winning 13 Super Bowls during their careers. Of course, that didn't really happen, but you get the point.

Ferguson's decision to retire as the manager of one of the world's most popular and successful football clubs has drawn strong reaction from all over the world, including the Prime Minister of Britain, who seemed to be grinning on the inside, hoping the manager's retirement might help the team Cameron roots for, Aston Villa Football Club.

Then came the reaction from Ed Miliband, leader of the Labour Party, who wanted his followers to know that beside being a great manager, Ferguson also was one of their own.

Cristiano Ronaldo, one of the highest paid players in the world, who played under Ferguson and now is a star at Real Madrid in Spain tweeted:

The news of Ferguson's retirement sent shockwaves around the world on Twitter, and triggered coverage from Bangkok to Mumbai. Earlier Wednesday morning, share prices for the American-owned football club dropped five percent on the New York Stock Exchange.

Just how popular is Ferguson? Take a look at this video which shows the reactions to his retirement on Twitter, compared to the reactions to Queen Elizabeth's speech earlier Wednesday.

Avie Glazer, co-chairman of Manchester United board, said in a statement that Ferguson will stay with club as the director. "Like all United fans, I want him to be a part of its future," he said.

With Ferguson's retirement coming at the end of the season, there is already a vigorous conversation on the Web about who is good enough to replace him. The club's legendary player Ryan Giggs says, replacing a manager like Ferguson is harder than replacing key players in the team. And as the BBC's sports editor asks, how do you replace the irreplaceable?

... whoever takes over already knows he faces a near impossible task to emulate Ferguson's towering achievements.

Ferguson's final game at home as the manager of the club will be this weekend at Old Trafford. For his rivals, it will likely be a day of relief. For his fans, it will be the beginning of a new era, because it is hard to imagine Old Trafford without Ferguson, his towering presence on the sidelines, chewing bubble gum for the entire 90 minutes, and screaming at his players and the referees.

Sir Alex Ferguson's bronze statue stands at Old Trafford. (Clive Brunskill/Getty Images)

You can read Ferguson's full statement here.

Disclosure: I grew up watching Manchester United and am forever a loyal fan.