[FMadera]

I'll give the real world answer.

Player gets into the sub zone, and comes back out before the whistle, warn her not to do it again, don't sanction. That said, you should be aware of things, and generally, once they step into the sub zone, whistle.

Now, if a team is out of subs, and a player is used to coming in, steps in, and coach is like NO NO NO, and player comes out of the zone quickly, don't look for trouble.

Just my thoughts.