They have to watch the BALL, in Lewis' interf. call he didn't even know where the ball was. So there is no breaking on the ball when you are watching the reciever and not the QB too.
Vereen has just been pure bloody diarrhea all year long. The lack of pass rush be damned, Vereen can't stay with anyone. If any WR that Veeren is covering even does the slightest jab step, Veeren will bite and leave his man wide open with no one within 10 yards.