Well...there goes all the excitement sucked out of the room. Another wasted debut due to being a sub.
I predicate what i am about to say by saying i hate the sub rule, but, having a young player (on debut even) as the sub makes sense. They are unlikely to be able to run a full game out effectively at this stage. Having them as sub means they don't have to. If they start, the plans to sub them may be impacted if an injury to another player occurs. You'd then end up effectively a man short when they predictably run out of gas.