Yes, we ran into that problem with a friend of ours who tested, he did not know baseball. In fact, our programmer didn't know baseball which is even funnier. We got him a diagram to explain it :3 Ideally I think we would do a short tutorial phase before you start play for real.
If you're interested, the way it's supposed to work is you have to bring the right color ball to the right color batter before he reaches one of those four little white plates he is rounding. You can miss him, so you have to go to a plate in front of him- thats when he will get outed and disappear (which is a little anticlimactic). He needs a little sad animation for when he loses, I think :)