that happened at my club Hearts a few years ago. we signed a player of undoubted quality but his head was fucked up,the club supported him,got him treatment,allowed him to go back home to recover from injuries,etc...we never really got to see the best of him but when he played (rarely) he looked quality. in the end we had to let him go,he was suffering a complete mental breakdown and was a complete loss to us,most expected not to hear about him ever again
that was Mauricio Pinilla,who has now got his head together and is showing that he is actually a very,very good footballer,god i wish he was not a nutcase when he was at Hearts,he would have ripped the SPL to shreds