If Diego can play as a second forward or as a wide midfielder in the 4-4-2 will be amazing. Part of my main concerns last year was that playing him as a trequartista messed up the rest of the midfield. A I saw it las season, Marchisio, Momo and Melo could not work as a triangle behind Diego, finding themselves out of position defensively or limited by their lack of technique(Momo) and Pace/Dribbling (Melo) offensively. They would work better as CM in a line of four, havind wide midfielders with more offensive duties.