They were playing Pittman by himself on one side so byu would shade a LB out wide to play underneath and take away the out route in a cover 3. He was also playing the flat so if USC ran a RB out into the flat the LB would play up on him, meaning a pittman sland would have been open all day. You saw it on the last play. Thats where the space was and they never made byu pay for it.
Harrell might be good but hes got some developing to do