Charlton is well aware of the threat that he poses.
"The club and its players have a great reputation. Above all, Cristiano Ronaldo. I have to stress that we never wanted him to leave Old Trafford," he told AS.
"The chance to go to Madrid came up, and it was where he wanted to go.
"He said he wanted to be the best player in the world, and he is. We have to find a way to stop him."