Lost the hunger of being a professional footballer IMO.
Played & scored goals in the Dutch Eredivisie, EPL, SPL, Europa League, UCL which included big money deals with Manchester City & Glasgow Celtic where he won trophy after trophy.
About 80 caps for Greece which included playing in two UEFA Euro & two FIFA World Cup tournaments scoring in the Euro 2012 QF against Germany & famously took Greece to the last 16 of the Brazil 2014 FIFA World Cup by winning & scoring the penalty in stoppage time to beat Ivory Coast 2-1.
He has been a professional footballer not only from the age of 16 away from home in the Netherlands but grew up in that environment where his father was also a professional footballer.