While I do not know or understand baseball or the terminology, I will answer this question to the best of my ability. I think that the most important player on the field would be the pitcher. If there's no one throwing the ball, if the ball is not in play, then there's no game happening. If the pitcher doesn't throw the ball, there's no ball to hit, there's no bases to run to after you hit the ball. I think the pitcher is the most important player on the field.