I am in my 3rd season of Juventus and have totally reshaped the squad. The only original players still remaining are Chiellini, Bonucci, Buffon(not used though),and Vidal (absolutely worth keeping). I still have Matri, Simone Pepe, and Luca Marrone, but the three of them have spent the last 2 seasons on loan. (Matri is fairly good and you can use him). Of course a lot of the players I sold are very good but I was able to get good fees. I didn't win anything in the 1st season, but won the league/Italian Cup in the 2nd and made it to the champion's cup final. In the current season I am leading the league and in the Italian Cup semi final.
You can sell Krasic for around 25 mil, he is a solid player but at 28 i think that is a good fee, I was able to get Antonio Valencia as a replacement for 1/3 of the price, and he ended up playing better.
You need a new left back ASAP - Paolo De Ceglie is a joke. I picked up Aly Cissokho and Sime Vrslalkjo (trained to play both sides) and both have been excellent.
Buffon still has one more very good year and about 2-3 decent years left, but I would get a new GK. I got Marc Andre Ter-Stegen (in the 2nd season) and he has been very solid, have led the league in goals conceded since I got him, he is not even 22 yet and I'm sure he will only get better.
Also, you can't get him until the 2nd season, but you co-own Sebastian Giovinco who is one of the best Italian players in the game and is currently averaging about 7.4 as a left winger on my team.
Other players I eventually bought include: Tevez, Sturridge, Gylfi Sigurdsson, Antoine Griezmann, Alberto Paloschi, Javier Mascherano, Ezequiel Munoz, Jack Rodwell, Kyle Walker, Eduardo (Croatian striker). I don't normally reshape my team this much but it has been fun and mostly a success so far with this team.