it sounds as if he is delofting the driver hence causing a low ball flight. Pulling the ball is from an outside in path. Would like at at one of 3 things
1) Grip - shutting the club face is usually caused by too strong a grip and may need to weaken it.
2) Ball position - should be aligned with the left armpit. It may be too far back in stance
3) Alignment - check to see not too far aimed to the right hence causing a pull. Hope this helps, mike.