BillyMac wroteIncidental contact is contact with an opponent which is permitted and which does not constitute a foul.
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ART. 5 If, however, a player approaches an opponent from behind or from a position from which he/she has no reasonable chance to play the ball without making contact with the opponent, the responsibility is on the player in the unfavorable position.
Bingo. From behind. No chance to play the ball. Unfavorable position. All the fixins for non-incidental contact.
This also falls under rule 11-1, "Call the obvious."