Manchester United boss Sir Alex Ferguson is baffled why Pep Guardiola left Barcelona. In pundit Guillem Balague's new book, Pep Guardiola, Another Way Of Winning: The Biography, United boss Fergie ­questions why he ever left Barcelona.

In a foreword to the book, Ferguson writes: "Whatever Pep's next move may be after he has taken some time out, whether he moves to the Premier League or not, there's always going to be a lot of speculation ­surrounding his future. He was at a ­fantastic ­football club at Barcelona and it is not going to get any better wherever he goes.

"Going to another club will not take any ­pressure off or ­reduce the level of ­expectation ­surrounding him.

"In fact, wherever he goes he is going to have the same ­experience: He is a manager, he has to ­decide what is best for his team, about ­choosing players and tactics. It is that simple.

"All managers' jobs come with pressure.

"I've been ­successful at Manchester United for many years and it's not without its problems - every hour of every day you have to deal with something. If Pep were to go to another club the questions would be the same as those he faced so far.

"It seems he reached a point in his ­coaching career where he was conscious of the importance of his job at Barcelona while he was experiencing the demands attached to it. I am sure he spent time thinking, 'How long is it going to last? Will I be able to create another European Cup winning team? Can I maintain this level of success?'

"If I had arrived in time to advise him I would have told Pep not to worry about it. A failure to win the Champions League is not an indictment of his managerial abilities or his team.

"I understand the pressure, though. The expectation was so high every time Guardiola's team played, everyone ­wanted to beat them."