The defender has a calf strain and is likely to be out of action for anything up to six weeks which effectively rules him out of the remainder of North Ends promotion campaign.
"As we thought at the weekend Callum Davidson has suffered a calf strain," manager Billy Davies has said.
"It looks as if it's going to be a four to six week job unfortunately so it looks as if we're going to be without Callum for the remainder of the games.
"It's a major blow for us and for him with the games we have coming up but we will keep our fingers crossed but it looks pretty serious, he's only just been able to put weight on it and he's hobbling around down at the training ground."