Bit of fun time.
The game now has seen many positions become very similar (if any difference at all). "Back in the day" there were notable differences like certain size per position etc.
In terms of the thread question I am meaning to a good level not just played that position in a team. eg Now Keith Mumby wasn't the most versatile but saw service to a reasonable extent at Full back, S/off and Loose Forward and played for GB in the Centre.