Allardyce told the News of the World: "Qualifying is more difficult because of the devastating injuries that Steve appears to be facing.
"There are so few matches and if the timing is wrong and you can't get the best side out there, you come in for criticism.
"It will not be any fault of Steve's or the players. The players will do as best as they can and, hopefully, that is enough.
"But if it is not we all know what is going to come." McClaren was dealt another blow yesterday when Sol Campbell was ruled out of Wednesday's friendly with Germany.