some analyst wrote a good blog about it recently
when pepe and marchisio were in fine shape, we were topping serie a, winning instead of drawing, beeing the best team in italy
when they stopt performing, the entire team went down two levels
so yeah, marchisio did make an impact. would be nice if he got more consistant tho.
and its not that he covers for vidal's abscence each game (if he is, he's playing more defensively)