A modern full backs job is to organise his defence be positionally aware and be safe under the high ball. In attack there main job is as a support runner hitting the line at the right time to create or support a break.

Murphy I am sure could be very good at this but something to look at for next season.
A fullback is not there for a kicking or passing game and there is only Brett Hodgson in super league who provides this but he is very much the exception.

But that's precisely the role grix is being asked to fulfil in our team!