Brown - Former first grader who came to the club WANTING to play first grade. He's impressed so far this year and can play wing or centre, on either side of field.
Lafai - Came up through the ranks to be promoted to first grade. Plays great at left centre, but has obvious defensive liabilities anywhere else in the backline (left wing or right hand side).
Inu - Can play across the backline like Brown, but due to an interrupted season with suspensions can't get consistency with games to work on his form.
Summary:
Inu and Brown are more versatile and offer more than Lafai. Lafai in his preferred position of left centre is great, however he's up against Morris for that spot, who is a much better player.
Morris will never lose his spot to Lafai, and Lafai plays best in Morris's position.
Simple really.