Christian is out of the clash with Wigan, and John says:
"He felt something strange with his knee in the first minute of the game against Reading, but comfortably carried on, and afterwards was a little bit stiff.
"Although nothing too untoward, the next day it had swelled up significantly, so he had an MRI scan and saw the consultant.
"The upshot of it is that at the moment it looks like he has had some sort of traumatic jarring of the knee where the two joint surfaces have come together and bruised one another.
"We will leave it for four or five days to see if the inflammation settles down, and review it on Tuesday or Wednesday of next week.
"At the moment there is no damage to any of the cartilage or the ligament, but there is a lot of swelling, which implies that he has jarred the joint badly.
"Once we get the swelling reduced and his range of movement improves, then it makes a physical examination more readily available - but at the moment it is an unknown quantity."
As for Steve Lomas, John says:
"He is doing well; it is just three weeks now since he sprained his ankle and he has been joining in with some football training.
"He obviously needs some games as he has missed some of the preseason games as a result of the ankle injury."
Don Hutchison is the other senior injured player, and John adds:
"I think we will be looking for him to have some part of the reserves' game next week against Norwich.
"Don had some swelling on his knee following preseason training and now it has calmed down he is doing a lot of strengthening work on the knee to try and improve the shock absorption and take a bit of pressure off the knee."