Walker says the players might need to drag supporters who have voted with their feet and left empty seats for previous European games at the Etihad with them all the way to the final.
He said on Tuesday: “It is down to us, as players, to create the atmosphere in there and help the fans. They are the 12th man (but) we have an important job on the field to get the victory and we need to make history for this club — and that is what we want to do.
“Obviously you do want the atmosphere, as it makes it difficult for the opposition to play when you have got the atmosphere. We do probably lack that a little bit but we have come to terms with that and we have to let our football do the talking."