In general the defenders are defenders because there limited in skill. Ok make not the centre backs because you need to be strong and tall. However I remember watching Ashley Young filling in a left back for a short period during a game and looked so comfortable. I thought blimey he's better than Bouma. Low and behold we have now seen some very technically gifted ex villa players do well in this position eg Milner Delph and Young.
I remember MON saying it doesn't mater what position you play you need to be good everywhere. In football you don't just stay in one place. I loved the way Barry Milner and Young could switch from left right and centre during the game and all help out defensively.
In my opinion were to hung up on positions and a bit out dated. We need good technical players all over the pitch. I'm guessing most defenders are defenders because there skills are limited. So why not put skilled players in defensive positions so we have quality throughout the team.
I know I've said this before and got laughed at but now some of the best coaches in the world are doing this as well. In the current squad Green would be great as a wing back if he had say Terry Chester and Collins as the back 3.
In fact buying Terry and Collins would solve a massive problem at vp.