In my opinion, teaching grammar without knowing grammar, which is what I understand that you are asking, makes no sense at all. Would you teach someone how to swim without being able to swim?. At the end of it, you may be able to float up in the water through some kind of moves but they will never be as precise as if you actually knew how to swim. I believe it is the same with grammar. Even though you may be able to learn some in your daily life, if you have never been taught grammar or you are planning to teach without knowing it, you are lacking a great and important piece of the language.