London - Alex Ferguson has criticised David Moyes for sacking Mike Phelan when he took over at Manchester United in 2013, accusing his successor of needing to prove his "manhood" by making "counter-productive" changes.
In his new book 'Leading', Ferguson also describes how United had Pep Guardiola in mind as a possible managerial replacement following the Scot's retirement.
"We chose David Moyes. He had been consistent in his job at Everton, had a good spell there, 11 years, and showed appetite," Ferguson wrote.
"I'm sure there are things David would do differently if he had the opportunity. Such as keeping Mick Phelan (Ferguson's assistant) who would have been the invaluable guide to the many layers of the club that (number two) Ryan Giggs is to Louis van Gaal today.
"There is no point suddenly changing routines that players are comfortable with. It is counter-productive, saps morale and immediately provokes players to question the new man's motives," added United's longest-serving manager Ferguson.
"A leader who arrives in a new setting, or inherits a big role, needs to curb the impulse to display his manhood."
Moyes' reign lasted less than a year but Ferguson has backed Van Gaal to succeed, citing the Dutchman's record.
"Louis has got a great background with Bayern Munich and Barcelona. He's got the pedigree," Ferguson told Sky Sports.
"He's got the experience. He knows how to handle these things."
Ferguson added that current Bayern Munich coach Guardiola passed up the chance to become United manager by turning down a request to call him.
"I asked Pep to phone me before he accepted an offer from another club (after leaving Barcelona) but he didn't and wound up joining Bayern Munich in July 2013," he wrote.
"When we started the process of looking for my replacement we established that several very desirable candidates were unavailable.
"It became apparent Jose Mourinho had given his word to (owner) Roman Abramovich that he would return to Chelsea and that Carlo Ancelotti would succeed him at Real Madrid.
"We also knew Juergen 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."