“Cannot sign player as not enough depth in position” Career mode problem

Hi, 

Im doing a Manchester United career mode as well as trying to make it as realistic as possible and when I try to sign Patrick Dorgu when I’m doing live score it says “ Cannot sign player as not enough depth in position “, I know this isn’t a bug or anything but it’s quite annoying and in real life Manchester United have signed him.

I hope you can resolve this,

Thank you,