Celtic manager Tony Mowbray insists the loss of first-choice full backs Andreas Hinkel and Danny Fox scuppered his side's attacking abilities in the 2-1 defeat by Rangers at Ibrox.
Fox missed out with a dead leg and a slight hamstring tear while Hinkel again failed to shrug off a knock leaving Lee Naylor to make his first start of the season at left-back and Mark Wilson keeping his place at right back.
Mowbray, who revealed Fox has withdrawn from the Scotland squad for the friendly against Japan next week where he was expected to earn his first cap, said: ''The big blow to me was the loss of full-backs because they are crucial to the way we play.
''I had neither of what I would consider my first-choice full backs playing and Danny Fox's left footed delivery might have been crucial. But we lost 2-1 so we take it on the chin and move on to the next game. Let's hope that in the next game we are talking about two totally-fit squads.''
Mowbray made it clear that even if he has a full squad at his disposal in the weeks ahead, he will make changes if his side's defending does not improve and it was in the centre-back area where he focused most of his concerns.
Glenn Loovens returned to partner Stephen McManus with Gary Caldwell left on the bench but it made no discernable difference as the Hoops gave themselves an uphill task by the loss of two early goals.
Mowbray said: ''Everyone has to step up to the mark because if we want to win the SPL more often and be a power in Europe, we have to develop and if the individuals can't step up to the mark then we will change them.
''None of my central defenders have established themselves as you can see by my selection. They have to stake their claim. There was an opportunity yesterday but did they cover themselves (in glory)?
''I don't think so but we move on. Football is about putting demands on your players and they either rise to the challenge of the demands or they don't. All of them have had opportunities and will continue to have opportunities.
''The day they keep clean sheets, and look solid and do well, the same two will play the next week.''