Pretty sure Arsenal were interested in Martin for a while after he looked the goods at Sochaux and was in the French side, but he transferred to Lille and it all went downhill from there. Probably at some minnow French club now
Odegaard had gone completely off my radar until I heard he came on as a sub in one of Real Madrid's pre-season games, only to be taken off 30 minutes later. Only 19 years old yet it felt like 5 years ago he signed.
I remember watching him years ago and thinking he looked really promising.
Milos Krasic is another that springs to mind. Once seen as one of the most exciting wingers in Europe, big money move to Juventus, played well there for a while and then it all went downhill. Now playing in Poland.