[PSU213]

First, a polite correction--players of the team that snap the ball are designated "A" ("R" is reserved for the opponents of a team that kicks the ball). A good way to refer to the offensive player in your situation would be "eligible receiver A1."

I'm having a little bit of trouble visualizing your situation. If they are on a "collision course" and the B player does not put his arms up, it seems difficult that the B player would block the vision of the A player without making at least some contact. Assuming, however, that this situation occurs as you describe it, I am not going to have DPI without contact unless the defender is clearly making gestures to break the receiver's concentration (i.e. waving his arms in front of the receiver's face). If he is just running near him and blocks his vision I have nothing, even if he is not playing the ball. As best I can tell, there is nowhere in the Rulebook or Casebook where the term "face guarding" is used (although Casebook play 7.5.10C addresses a non-contact DPI foul).