Former general manager Jock Brown has warned incoming Celtic chief executive Dominic McKay that he must quickly get to grips with the size of the club.
The Murrayfield chief operating officer will leave his SRU role in the summer and faces a mammoth rebuilding job in Glasgow's east end.
A new manager will be needed and a director of football also expected to be identified ahead of next season in a huge summer for the club.
However, Brown told BBC Sportsound that the biggest tasks facing McKay while he adjusts to life at Celtic.
He said: “I would say to Dominic McKay, and I wouldn’t presume to tell him anything because I’m sure he will have done his homework throughly and will know exactly what is involved, except for one thing.
“Now I’m brought up in the west of Scotland and have been here all my life really, and I did not appreciate how big Celtic was.
“Until you are in there to realise the size of the club, the international interest in the club and the reaction of supporters to bad times, which we are seeing right now, the reaction is just incredible, and you can’t possible know that unless you are in there.
“That’s all I would say to him, understand as quick as you can how big the place is.”
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With a replacement for Neil Lennon top of the agenda for the club, Brown admits the club will need to be careful in the appointment.
The gaffer must be on the same page with any new structure put in place and share the "vision" of the Parkhead hierarchy.
Brown explained: “You can’t change anything unless there is consensus at the right levels.
“It’s vital that Dermot Desmond is happy, it’s vital that Dominic McKay is happy, the chairman Iain Bankier is happy, Tom Allison is happy and they are all pulling in the same direction and agree what the vision is.
“They have then got to work out the strategy to bring that vision to pass.
“It’s impossible if they are not all pulling in the same direction to bring in a director of football who buys into what they want to do, and a head coach who is on the same page.
“If the guys got a huge ego, a Jose Mourinho for instance who would want the final say in everything then the club might say that’s not for us.