The meeting with Ferguson might have gone wrong for so many reasons.
Ferguson might have said something along the lines of "Right, Park is getting a wee bit old so I need another one of you small fellas to stick in there when the going gets tough. You're all disciplined and you work very hard on the field."
Or maybe they met in a Chinese restaurant in an attempt to make him more comfortable ("See? It's just like at home").
Another possibility is that Kagawa didn't understand a word of what was being said in that thick Scottish dialect and went home disillusioned.