Maybe ask the player to approach the various sources of good ball i.e. ruck; scrum; tackle from a much lower position. Ask why this might be a good idea, and see if you can get him to come up with the answer. I'd be hoping that he would work out that his play is more difficult to predict for the opposition if he is hidden behind his players who form the breakdown. Maybe organise some practices where the defence is guided by the coach, but the guidance mechanism (coloured cones; hand signals) is unable to be seen by the 9. This would mean that what he does could need to be directed by the 10 or 12. Play a guided game during which his team; in possession; cannot score until the coach gives the command to. 'Keep ball' is going to be putting him under pressure to ship the ball to team mates. Maybe also take them 10m. back when he's caught in possession. An alternative may be to describe the scoring area of the pitch as between 2 cones 10m. apart out right corner and/or out left corner, on the tryline so that he begins to understand that the ball travels faster than he can run. Conditioning the defence will work.