A President Taking the Fifth

Here's a question that I thought I'd throw out for discussion. Let's say that one of the civil suits against the President leads to him being deposed. In that deposition, he is asked a question and decides to assert his Fifth Amendment privilege against self-incrimination, which is his right. Wouldn't such as assertion be a tacit admission that the President believes that he cannot pardon himself? If he could pardon himself, then how can he take the Fifth with respect to a federal investigation?

UPDATE: Upon reflection, I see that in practice it would be hard to separate statements that could only self-incriminate for federal crimes (where the pardon power applies) as opposed to state crimes (which the President cannot pardon).