Fergie, the Godfather of football managers, admires the way his friend has consistently defied his critics - including the way he has revitalised the struggling Hammers and guided them back into the Premier League.
Ferguson said: "He went there a year ago, the cynics were out there saying he's not a West Ham manager, doesn't play football. What was his mandate? To get them up to the Premier League as quickly as he could and he got them up in a year.
"Tell me someone else who could have done that.
"Also, he had to get rid of two or three players because of the salaries they were on and rebuilt the team.
"He's very underrated.
"Bolton and Blackburn have been relegated since he left them and Blackburn was one of the craziest things I've ever seen. The people that came in took the advice of an agent - it was so stupid."