What would happen if, before a snap, the 12th man on the field realized he needed to get off the field, and rather than running to his sideline, he stepped off onto the opposing team's sideline? This all occurred before the ball is snapped, so it happens timely. However, the player technically exit the field when he wound up on the side opposite his team? Could the opposing team prevent him from stepping onto their sideline, for instance, by pushing him back onto the field or impeding him from stepping on the sideline?
Article 6 A player or players who have been replaced must leave the playing field or end zone on their own team’s side
between the end lines prior to the next snap, free kick, or fair-catch kick.
and
Article 8 Penalties for illegal substitution or withdrawal are:
...
(g) For a withdrawn player clearing the field on the opponents’ side or across an end line: Loss of five yards from the
previous spot.
THAT!!!!