This is a big deal for ESPN leagues. In ESPN leagues you need to start 3 games or make 5 appearances for position elligibility. If a player reaches those requirements, not only are they elligible for this year, but they will also be elligible at that position the next year.
So in Huff's case (who I drafted this year in a keeper league), he was already elligible at 3B for this season. Two more starts at third, and he'll be elligible there next year as well.