Most effective rotation of players on a team?

The only purpose to rotating players is to keep them fresh. Teams with smaller D-lineman, like the colts, rotate so they don't get worn down by larger O-lineman. Rotating QB's only makes sense if you don't have one good one. Teams are trying to make sure that they have a solid backup at RB to keep their #1 guy fresh. You don't want to go into the playoffs with tired legs. Just ask Larry Johnson!!