I would argue that hitting a baseball is as much a mental game as it is hand eye coordination. Yes you have to have great hand eye coordination but even with these skills people will get into slumps and once that type of thing happens they are difficult to get yourself out of.
Now that said, steriods not only alter your physical mass, they alter your mental state. I played ball through high school and college and know lots of people that have juiced. Never tried it myself but they have told me multiple times they felt great when using. If you are playing ball and feel like you can do anything then you often can.
People with increased amounts of testie in the blood stream have been shown to feel better/more confident about themselves. This could also help the mental game of hitting. Just putting that out there.