Not sure that's the case at all Chops. Trying to think how many times we've seen 3 at the back under Rodgers so far, and I've got Everton twice, Chelsea, Anzhi away (also may have at home?) and Fulham away in the first half. In that time I think we've conceded 3 goals, one of which was from a corner. Not sure it stands up to be honest. Depends how you use it.
To be honest Juan, the 3-5-2 poo-poo is a hidden swipe at some esteemed posters(and not so esteemed moderators *you know who you are*) in here, regarding the system.
I've been an advocator of the system for over 3 season now and in the mean time, our personal hasn't changed that greatly to make me think why we shouldn't adopt it more often, if not all the time.
As we stand now, our fullbacks aren't full backs, well, not good defending ones anyway and our centre halves aren't just plain old stoppers - though Carra(did), Toure and Skrtel have that theme to them.
Far to may people think 3-5-2 = 5-3-2, it doesn't - it offers what we've been lacking in ages in attack(circa 2 years ago and beyond and now even) which is numbers in attack.
Cut to today and Rodgers plays more with an attack mind, but he must really get to understand what he has if he wants to adopt a 3-5-2 system.
For me there are two foils(in my opinion) in a 3-5-2 first one is the back 3. In which I'd play a Kelly a Toure an Agger, even a Skrtel in there, defencively mobile players. Mobility being something I think Rodgers adores.
Then, give our two Fullbacks(I could think of more derogatory words for them) more of a licence to roam, which, is what they pretty much do now anyway, but allow them to be able to assist in the middle with a Lucas and Gerrard who in turn, act as another foil for Coutinho to reap fire and damnation on the opposition
, with a Sturridge or an Aspas or even a Suarez to slot.
Two foils complementing one big system.
Easy this football manager thingy isn't it!
All in my humble opinion of how we should play a 3-5-2, and don't forget - I'm either mental, or a complete mental genius. I think the former.