Fabio Capello claims Sir Alex Ferguson told him he decided to retire as Manchester United manager due to stress and because, at the age of 71, he still wants to travel the world.

The former England manager said: "I called him yesterday and he told me he has decided to go now because there is too much stress nowadays. Always having to win something is very challenging, and he told me he wanted to go around the world with his wife.

"His secret is amazing. To have that strength and ability to change things and improve every year, and always have the same desire to win."

Capello was taken by surprise at the announcement. "I met him a few months ago and he told me he would carry on," he said. "So the news of his retirement surprised me".

Ferguson's old sparring partner Arsène Wenger felt English football would not be the same without his rival. He told the club's website: "I would just like to pay tribute to an unbelievable achievement and a fantastic career.

"Basically the achievement is immaculate, when you look at the whole structure and consistency of the achievement. It is something exceptional. It is difficult to imagine English football without him but it's now a reality and a fact.

Wenger thought David Moyes' task in filling Ferguson's shoes to be a difficult one. "It's a great void to fill for Manchester United, because the charisma and personality disappears suddenly in a club which has been dominated by it for such a long time. It's not an easy task to replace a person like that."

Sam Allardyce said Ferguson had been a major help when the West Ham manager was starting out in management two decades ago: "He has had huge influence on me. I got to know Sir Alex when I was at Notts County when I was invited on to the LMA [League Managers' Association] committee.

"I have been managing for 20 years now and a lot of that has been phone calls when you are in a pretty dark place in this game as a manager. You need some advice and you need to know who to turn to, and that solid advice would always come from Sir Alex if you rang him."

Harry Redknapp has been doing battle with Ferguson in the Premier League for the best part of 20 years and believes his retirement will leave a big hole in the game. "He will be a great loss to the league and football," he said.

"He is a fantastic manager, but a top bloke as well who always had time for young managers if they phoned up – no matter what level they were at. I always spoke to him and enjoyed his company, and he would have been a big influence on a lot of the younger managers.

"It was an amazing achievement what he did – taking over one of the biggest clubs in the world going through a difficult period and then started winning championships and everything else he could win."

The Queens Park Rangers manager was also quick to praise the appointment of Moyes at Old Trafford: "He's the prefect choice and I think it is good that they have taken a British coach and have given him a chance. They have not just gone abroad but taken someone who has done his apprenticeship. It gives great hopes for everyone out there in all divisions.

"He has worked his way up the ladder and did a fantastic job at Everton."