In his new book "Leading", United's longest-serving manager outlines the selection process behind Moyes' ill-fated appointment at Old Trafford, which lasted less than a year after he replaced the retired Ferguson in 2013.

"I asked Pep to phone me before he accepted an offer from another club but he didn't and wound up joining Bayern Munich in July 2013," Ferguson wrote.

"When we started the process of looking for my replacement, we established that several very desirable candidates were unavailable.

"It became apparent that Jose Mourinho had given his word to Roman Abramovich that he would return to Chelsea, and that Carlo Ancelotti would succeed him at Real Madrid.

"We also knew that Jurgen Klopp was happy at Borussia Dortmund and would be signing a new contract. Meantime, Louis van Gaal had undertaken to lead the Dutch attempt to win the 2014 World Cup," he added.

Moyes was sacked after 10 months at United but Ferguson defended his fellow Scot's record prior to joining the club. "We chose David Moyes. He had been consistent in his job at Everton, had a good spell there -- 11 years and showed appetite.

"Unfortunately, somehow it didn't work out for David. The process was perfect. It was a good process," Ferguson said.

Instead, the former United manager reserved his criticism for Moyes' decision to overhaul his backroom staff after taking charge. "I'm sure there are things that David would do differently if he had the opportunity to relive his time at Old Trafford," Ferguson said.

"Such as keeping Mick Phelan (Ferguson's assistant), who would have been the invaluable guide to the many layers of the club that Ryan Giggs is to Louis van Gaal today.

"There is no point suddenly changing routines that players are comfortable with. It is counterproductive, saps morale and immediately provokes players to question the new man's motives," he added.

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