his forehand approaches were really bad because he would stop, hit then come in vs guys who would hit while moving forward. The latter approach allows you to get 2 or 3 steps closer to the net. Watch sampras forehand approach, edberg on the backhand slice they move through it while hitting so the close so much better.
https://www.youtube.com/watch?v=vlD1w6mu61o
The difference between closing on not closing is the difference between a good penetrating volley vs the Roddick block it into the court. His movement forward was just really bad, even off the serve.