To be quite honest, does this make any sense at all ? Rodgers already knows which formations he can/can't use because he tried them all out last season and before at Swansea, so do the question is do players know the systems and can they adjust ?
At least half the team at least certainly do, the others are maybe not quite so familiar (though will no doubt have learnt them to a degree in pre-season and in training) so there will be a short period of adjustment whilst they learn the different formations but it's hardly rocket science and they may even have played similar systems at their previous clubs.
You also have to take into consideration how many matches will be played in Europe and when they start. The new players may already have fully adapted by the time they come around.
This sounds like many of the excuses being made for a potential Liverpool demise that I'm hearing, most based on wishful thinking or wanting to fill column inches / blogs and podcasts, I mean what else is there to discuss in pre-season