If one of my slower players does indeed get pinch run for, how would "Sparky" determine who would take his place in the field in the following inning? Do I have to assign a defensive replacement on the "Defensive Replacement Hierarchy" page? Or will "Sparky" do it for me?

For example, I have 1971 Graig Nettles playing 3rd. I drafted him basically because of his glove. But he's slow. If he's lifted for a pinch runner late in the game, would I have to assign his replacement in the "Player Rest Hierarchy" or the "Defensive Replacement Hierarchy"? Or not worry about it because "Sparky" will install his backup? I don't want Nettles pulled late in a close game because he's one of the best fielders out there.

getting the right replacement after pinch running is a tricky one.

it will only go the defensive replacement hierarchy if the conditions for a defensive replacement are met, which means you have to be winning the game, but typically the sim will not pinch run if you are winning, so this doesn't happen often

if the pinch runner also has a third base fielding rating then that's who will play third base, even if its someone with a D-/D- rating you really dont want playing there. if the pinch runner doesn't have a third base rating, then it will put in someone who does have a third base rating, but i'm not exactly sure the logic of how this works.