"Chris is really struggling and, typical of the professional he is, he played with it for a long period of the game on Saturday," says Peter Grant, explaining the nature of Chris' problem.
"He feels as if he is letting you down if he comes off in the game - that is the sort of character he is.
"He felt it before half time but he said he was okay to continue, and that is the sort of person you need; he has that winning mentality and wants to be involved.
"When things aren't going particularly well he wants to put his arm to the wheel to help you out."
Peter says it is not easy to say how long Chris will be out and adds:
"It is difficult because some days you can wake up and it is fine, and others you don't feel anything, but you have got it.
"Sometimes you need to take part in the game to see if you are fit."
But Peter says that Rufus has a good chance to stake his claim again and adds:
"To be fair, Rufus has been excellent because Chris came in and obviously plays the same position; his training has been excellent even though he would have been disappointed.
"Football can change quickly and if you let yourself down in training when you are not selected you are the only one that is going to suffer because you will be unfit and not up to speed - then, when you get a chance people will say you are not good enough to be in the side.
"But Rufus has been spot-on and he has this opportunity to come in."