It's actually quite simple. We build a box around the entire field. The referee is outside the box. A player running in the box throws a pass. Until the referee looks inside the box, he doesn't know whether the pass is forward or not. Therefore the pass is in an indeterminate state of being both a forward pass and a legal pass, or strictly speaking, the waveform describing the pass is indeterminate. This is known as a "Schrodinger pass".
The philosophical implications are more difficult. If you adhere to the Copenhagen interpretation, then the pass does not exist until it is observed by the referee. If you are more of a "hidden variables" man then the pass was always either forward or legal but you didn't know which until it was observed by the referee. Thos poor fools who favour the many-worlds interpretation think that there were an infinity of universes with an infinite variety of pass and the observation by the referee determines whether we are in a universe in which the pass was forward, a universe in which the pass was legal or a indeed a universe in which the ball transforms into a seagull who befouls the referee beforing flying into a mauve sunset. The most rational of us subscribe to a minimalist interpretation in which the philosophical implications are so much horseshit and the waveform is a statistical process that doesn't apply well to a single particle, or a single football in this case. Strangely enough, there are weider interpretations.
If you wish to know more, and who wouldn't, I recommend reading both the IRB Laws and a suitable quantum mechanics book simultaneously (such as In Search of Schrodinger's Cat and Schrodinger's Kittens by John Gribbin). Remember that it will only work if you read the books while in an inertial frame of reference.
