As far as the "position"-problem goes, i don't think he will make that much of an impact in (for example) nocerino's role. In Mali, he played his last game on the left side and did a solid job. I think he can cover some more roles, as just DM. But afterall, considering how many bad passes nocerino made yesterday, i think sissoko can be a good improvement. Let's just see. The fact that we will not necessarily NEED him to play as fast as possible, but that we can implement him sooner or later may add a positive effect to his evolution