Crerand pities Ferguson's successor, claiming his fellow Scot will be a tough act to follow.
"I'm just stunned," said the 1968 Manchester United European Cup winner. "God help the poor fellow who's going to have to follow him because the standard he has set is incredible."
Crerand suspected Fergie was planning his farewell when he signed Robin van Persie last summer.
"It entered my head, but then I forgot about it as I thought he would want to win the European Cup."