For sure Sir Alex Ferguson really did a great job while in his duty as Manchester united head coach winning 13 premier league matches for Manchester united and also won two UEFA champions league titles and about five FA cup. This record kept by Sir Alex Ferguson is the greatest any coach has achieved in the English premier league. Indeed Ferguson will always be remembered for his great impact not only to Manchester united but in football history at large more of his kind are very rare.
No one doubts Sir Alex Ferguson's ability. I really agree with you, that Sir Alex Ferguson is a successful coach who holds the position as coach of the Red Devils. Sir Alex Ferguson is able to find young talents who to this day have become classy players like CR7 and many others. Moreover, even clubs out there are reluctant to meet the Red Devils, because the tactics implemented by Sir Alex Ferguson are able to make English Premier League clubs and clubs in the Champions League avoid him. This is why Sir Alex Ferguson has never been replaced by a coach. The current Red Devils only have a large salary but have no impact whatsoever on the club they hold.