So, these are our rules for scoring...
Scoring
Each team's total score is the accumulation of points attained by the eight players selected or the appropriate interchange player/s.
* Forwards - 4 points per goal, 1 point per behind
* Midfielders - 1 point per disposal
* Backmen - 2 point per mark, 1 point per tackle
* Ruckman - 1 point per mark, 0.5 points per hit-out
I still don't understand how the sub is an issue. It might be, but I don't get the point you both are making. You pick the eight players who get their scores from the Final Siren stats. If, and only if, one player you name doesn't take the field as the 22 (or 23 including the sub) you get someone from your interchange whose score will count.
If you select a player who plays a quarter or so and leaves the field due to injury, tough. You get those meagre points.
If you select a player who only makes the grade as the designated Sub for the game and only gets onto the field at 3/4 time and so scores little, again, tough. That is the best you can score.