Scholl told The Guardian: "He's very strict and severe. So the players just have the chance to follow him or they are out, and he takes the next players.
"He's very good with young players. I think everywhere he was, he had some problems with big players and the staff."
Manchester City chief executive Soriano told ESPN: "He is very tough, people don't like him, but he wins. And one day you don't win - and when you don't win, everybody that is angry with you will come back to you and try to kill you."
It has been widely reported that Van Gaal will be announced as David Moyes's successor at Old Trafford over the coming days.