Parts for Whirlpool washer leak

Checking the parts list, for a leak out of the center bottom of my wash tub.The main outer tub seal is offered. I do not see a part called the Agitator or center shaft seal. It is about the same size as the outer tub seal. Could you tell me if that part is needed? ( I was looking at another site and saw that part, but they could be wrong). What parts do you recommend for this type of leak?