I don't know what kind of defense you're running, but when I play man coverage and my safety is supposed to cover a WR in man, he lines up across from him. I don't have to manually put him there and he doesn't sprint to the middle of the field at the snap of the ball. I'm on 360 if that matters (but I can't imagine why it would for this).
(The FS is the dude over the slot receiver in these pics)
3-4:
Nickle 3-3-5:
Nickle Normal:
Dollar: