Porter has been unlucky with injury at Derby.
Rosco was dynamite when he first joined Cardiff, but has fallen away quite badly.
I would also think most players don't expect to move to a bigger club and expect it not to turn out well.
I mean imagine you were working for a wee local shop as a store manager and John Lewis called saying they wanted you to run one of their stores. The first thing that enters your mind its Yass I have just got an amazing job, not mmm I might not take this as I could fuck up.