[KCRef]

B1 scores a basket, and A1 throws in to A2. A5 is jogging up the court (still in his backcourt), looking back at his teammate with the ball. B5 is facing A5, and has obtained a LGP with plenty of steps infront of A5. A5 collides into B5, and they both go down. Is there any foul? I say no.

I believe that it would be similar to when the offense sets a blind screen for his teammate that has the ball. If the defense never sees the screen, then there is no foul when they collide.