Charlton describes Ferguson as a "genius".
"It's a game everybody tries to play with me," he told the Daily Mail. "The one about how long Alex Ferguson will stay. As soon as I finish talking to someone, they always ask it. It doesn't matter who they are.
"How long will he go on for? When will he turn it in? The answer is that I just don't know. The other clubs are hopeful that it will be soon, no doubt. But he's a genius the way he handles the players and looks after the players. He's unique.
"I go to every match and I'm amazed at the number of times that a player does something that Alex has taught them. These players, they don't forget. Everything Alex tells them, they take it in.
"If I was going out of the trenches he is the one I would want beside me. Nobody else. He has something inside him that everyone else wants."