He was a big hope when he was a Junior, but then didn't take his career very seriously, wasn't really focussing on tennis, he even considered giving up on tennis at a time. The turning point was in Wimbledon 2006 according to him, he realized he was just wasting his talent and should really give it a try again.
That's why he's such a late bloomer.
I translated a portrait of him in the German tennis magazin at the end of 2007:
http://www.menstennisforums.com/show...&postcount=408
http://www.menstennisforums.com/show...&postcount=409