not my article of course . but this article talks about the 1-1 serie A roma game, and guarin's role.
imo guarin is undertaking the same role boateng had last year in milan that of a "driver". His position is the same as an AM, but he's not a conventional attacking mid. He uses physicality, speed and dribbling to bring the ball forward from the 4-3 to the front 2.
I think Guarin is doing the same thing. We've all complained about strama's 7-3, 8-2 formations. and the front strikers being completely isolated from the central midfielders and defenders.
now hes changed the formation to a 6-1-3, 7-1-2, relying on guarin's dribbling and speed to bring the ball to the forwards. one quality of guarin i never noticed was dribbling. whoscored.com rates dribbling as his top quality ( http://www.whoscored.com/Players/22701/ ).
that's why he was extremely tired in the game against roma. you could see that even his mental state took a hit, because of his physical tiredness. this position is extremely exhausting, as unlike a conventional attacking midfielder who uses passing as the connection between cms and def and strikers, he uses his speed,physicality, and dribbling to make that connection, which can take a toll on you.
as long as strama's midfields are crappy and unorganized, without the right personnel, keep expecting to see guarin in this "attacking midfield" role.