Wigan chairman Dave Whelan believes Sir Alex Ferguson is the only reason Manchester United have averted a crisis during the Glazers' ownership of the club.
The Glazer family took over at Old Trafford in 2005 but, despite growing fears about the size of their debts across their businesses, Ferguson has won numerous trophies in that time including three league titles and the Champions League.
United were only able to clinch the Carling Cup last season but, for Whelan, it is essential that Ferguson remains in charge if they are to remain successful in the coming years.
"There was talk of Sir Alex retiring last year and the year before and he hasn't done it," Whelan told Soccernet. "He is just unbelievable in what he does.
"His energy, his enthusiasm, his passion for the game and for Manchester United has not waned. He is still the first at the training ground every morning. I've always found him the perfect gentleman, and I hope he stays on as manager of Manchester United for another four or five years.
"He still produces fabulous football teams, playing fantastic football, and for me he is the most important person at that club.
"Manchester United have remained right at the top throughout all the troublesome years under the Glazers, and there is a simple reason for this - and it's down to only one man."
Whelan believes Ferguson has outstripped Sir Matt Busby's achievements and can now be considered the best the game has seen.
"I feel he is the best manager ever," he said. "He has emulated Sir Matt, surpassed Sir Matt, and even at his age he retains such incredible energy - his enthusiasm for the game burns just as bright as ever.
"It is going to be enormously hard to fill Sir Alex's boots, I can tell you. I can see someone like Jose Mourinho coming to Manchester United, and he would certainly be colourful, and it would make life interesting, but there is only one Ferguson."