Ok, I understand two things from the USSF position papers about offside and the AR’s job to make the call:
1. After the ball is played and there is an offside player and an onside teammate running towards the ball and the onside teammate has a reasonable chance of getting there first, the AR should not make the offside call unless the offside player touches the ball first.
2. Independently of the first item, there is a situation where an offside player (only) and a defender are running towards the ball. If there is potential for physical contact here, the AR should make the offside call for interfering with an opponent.
Now, my hypothetical scenario is this. Let’s say there is two teammates running towards the ball, one onside and one offside. Both have an equal chance of playing the ball first. According to guideline #1, the AR should wait until one of the players has touched the ball. But what about when a defender (or defenders) also run towards the ball? Should the AR immediately flag the offside? Should the AR decide if there is potential physical contact between the offside player and the defender before making the call? In this situation, should the AR just wait to see who gets the ball first?
USSF answer (May 31, 2007):
To quote a recent Federation memorandum, “In situations where an attacker is coming from an onside position and another attacker coming from an offside position, each with an equally credible chance of getting to the ball, it is imperative that officials withhold a decision until either it becomes clear which attacker will get to the ball first (even if this means having to wait until one or the other player actually touches the ball) or the action of the attacker coming from the offside position causes one or more opponents to be deceived or distracted.”