Was he the only one? The team look unbalanced until Allegri reversed to 3-5-2. The team and players underperforming in the first few months was on more on Allegri. IMHO
Injuries as well played its part, where it's difficult to show your best when you have Padoin and Sturaro by your side, as opposed to having both Marchisio and Khedira. If the roles were reversed and Marchisio had to play with aforementioned duo, it would hardly be any different.