The reasonably accepted view is that you don't change your defence too much. So in the first game we picked up injuries to (if I recall) Riise and Carragher.
This meant having to bring Aurelio in way too early. It also meant that in the Sheffield United game, for example, there was no scope to change the attacking options which were clearly not working 100% because the two defensive injuries only allowed one positive change.
Combine this with the fact that players were knackered from the world cup (Gerrard recently admitting this about himself, and it wouldn't be unreasonable to assume the same about Alonso and others).
If we don't go overboard and sign a gazillion new players (which some on here would seem to advocate) such that we can start with a fairly settled squad, then rotation will not make one jot of difference to the start of the season. It will make a huge difference at the end of it though.
What we need is a squad that is largely familiar with each other and the demands of the coaching staff. We have that and if it is augmented by two or three new signings (possibly with additional youngsters to strengthen the reserves if needed) then I think we will start the season well. An example of this can be seen with Mascherano. The squad (not the team) is fairly settled now and it means we have been able to bed in a new signing with reasonable ease.
Rotation is as much of a red herring as zonal marking is, I believe.