If Juventus wants to devote itself to the 2 defensive CM style, it would be prudent to have a world class DM who is young and has room to grow further and can actually pass. Zanetti isn't getting any younger, Nocerino might be a little too raw still for major competition, Tiago has yet to prove himself to Ranieri full-time, and Marchisio could have the same issues as Nocerino. Having Mascherano would mean one CM spot is rock solid, and the other could be split between Marchisio, Nocerino, Tiago and Zanetti, depending on form. Most of those four alternates can play other midfield positions.
Mascherano, Van der Vaart and Barzagli/Pasqual would be my ideal Winter/Summer market.