Potential blocker or not?

[Illini_Ref]

Read 9-2-3(d) and tell me where in that rule that it only applies downfield.

The case play references a block. That infers that the offensive player is still a potential blocker. No argument here.

I maintain that a back (eligible receiver) who is turned and about to catch a pass is NOT a potential blocker any longer. Say the defender gets around him and wipes him out. First of all, that is a tackle of someone without the ball which is holding (a tackle does NOT have to be a wrap up). Second, contact with an eligible receiver that is no longer a blocker is illegal.

If a receiver is downfield but the QB still has the ball when the receiver is hit from the side and knocked down, is that a foul? Can't be PI but of course it is a foul. Why? Because the receiver was no longer a potential blocker.