Oh come on maaan!!
The problem is deffinetly in the midfield. The few mistakes that were done in the defence i think are coincidance. I dont think that the defance is the problem. REALISTICLY every single time i watch Juve play we are either attacking from the wings (and we all know that Neddy is not playing well and Marchionni is not so goo) or playing stupid ass long balls. Now, playing long balls is not so bad when you have players that can do that but with Marchisio and Sissoko we can not afford that because REALISTICLY they suck at long balls. I also think that paying with 2 DM's is a pretty stupid and pussylike idea. Yes we defend well but tell me what difference does it make when you cant form a decent attack and score a goal?? So bottom line i think that the problem is the 2 DM's from which one has to go (not Sissoko). If we have Sissoko and we buy a good midfielder (Xabi Alonso) the problem will be solved. Then we will have more options in creating nice attacks(we could attack from the wings, if that doesnt work we can play long balls and if that doesnt work we can attack right through the midfield) and we will also have a solid defence since Sissoko will be there doing a "Makelele"
P.S. I still, to this day, think that we should have given a chance to Tiago.