Hi there, thought I'd shed some light on this. In short it's both. If the player is already comfortable in that position, they will focus on those key attributes for the role (they will also develop in other areas, but these attributes will be the main focus). If they are not already comfortable in that position, they will start learning the role and their ability to do so will depend on their versatility, personality etc etc (so keep in mind that just because you ask a player to learn a new role, doesn't mean that they will be successful, or be happy about it).