So I recently ran into a glitch in my career mode where the ball decided to just become invisible.
FIFA 13 invisible ball (via ndeddiemac)
No matter how many times I tried to sim through games, restart, reset, etc, the ball was gone forever in my career mode. If you have this problem, ends up it's an easy fix. In the pre-game option menu (play match, team management, etc) if you go to game setting you can change the ball. Just a helpful tip for anyone that runs into it.