Ferguson was at the helm from 1986 to 2013 and during that time, accumulated 13 Premier League titles, 5 FA Cups and two Champions League titles.
The current Red Devils boss Mourinho recently acknowledged that it was unlikely he would finish his career at Old Trafford, stating: "I ask how is it possible in modern football that any manager is going to last 15 or 20 years in the same club? I think [Arsene] Wenger [at Arsenal] is the last one to do that."
And although Knox, who was an assistant to Sir Alex in his first six seasons at United, agrees with the Portuguese's sentiment, he says that the lack of longevity is the precise reason why Mourinho will never eclipse the achievements of Ferguson.
"The only thing you can say about him [Mourinho] and Sir Alex, they've both had phenomenal success," Knox told Tribal Football.
"The difference in their success is that Fergie built the club from nothing up to winning all these titles and the Champions League.
"Mourinho, apart from Porto, has gone to big clubs and he has been able to recruit top players, but Alex built United from scratch, when there was no money to buy players. He continued with the youth policy and believed in the youth players coming through, there's the difference there.
"[It] was a long term project and I think everybody at Manchester United recognised the amount of work that was put into bringing these lads through, and the club knew it was going to bring success sometime in the future and eventually it did, so the difference is Alex did that from scratch.
"Jose went into teams and obviously controlled the teams well and his style of football suited the club he was at, so both have had fantastic success, but I don't think Jose or any of the other [managers] apart from Arsene Wenger are going to be at a club for 27 years."
Archie Knox is currently promoting his book, The School of Hard Knox: The Autobiography of Archie Knox, which chronicles the life and career of the man who assisted Sir Alex Ferguson at Manchester United and Aberdeen, Walter Smith during the nine-in-a-row era at Rangers, and Craig Brown for Scotland, amongst many others. The 70-year-old has seen it all and is one of the most respected and admired coaches in football.
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