Turan had a spectacular defensive performance in midfield. He intercepted, tackled and recovered the ball at will during his entire time on the field. With both him and Alves on that right side, the opponents are in serious trouble when they possess the ball on that side in their defensive half of the field.
Turan was a mixed bag on offense. Just like almost all new Barca players, it is going to take him at least half a season to learn how to really fit into the offense. But, so what: if he is just OK on offense, he is so incredibly good on defense that he improves this team a lot.
With the quality of Iniesta, Rak, Turan and Sergi Roberto, these four cannot be confined to just sharing two positions. The team is going to have to have more than two of them on the field at the same time. Forward, DM, fullback, I don't think it matters that much where you put whoever is not starting in midfield, they just have to be on the field. I don't want to see mediocre players like Munir, Samper, Douglas, Adriano, or LB Mathieu play any more this season: play these extra, super midfielders instead.