It depends completely on how you define a "field." The point of having an advisor is that s/he can help guide you for the first year or so and teach you "how to research." You probably won't be doing groundbreaking stuff to start with so it wouldn't matter that much, but later, when you do start properly researching, you need someone who is familiar with the sort of research you're doing, in order to help you. However, without an actual scenario, there is no way to answer the question.