Managers play a very important role in setting up tactics and strategies for a match, especially in Champs League. Mellor, Sinama-Pongolle, Xabi Alonso, none of those are Champs League experienced. Biscan? Traore? Baros? Finnan? Riise? Le Tellac? These are all have fuck all in Champs League experience. Torres have none, Mascherano never played in the Champs League when he played for us. The difference is Rafa who knows what it takes to not lose games in the Champs League and setup teams to go through the motion. Players may be the one executing the tactics, but if you got it wrong - benching your most experience player in a match against Madrid for example, can be detrimental.