James Hanson's ever-present league record is threatened by injury.
The City target man is troubled by a tight calf, which makes him a doubt for Saturday's trip to Peterborough.
Raffaele De Vita is also struggling with a thigh problem while Caleb Folan remains out with a sore hamstring.
Boss Phil Parkinson said: "I'm not overly concerned with any of the three long-term but they are doubtful for this game.
"If they aren't fit, someone else will get an opportunity. As I've said, the whole squad is going to be utilised over this Christmas period."
Youngster Oliver McBurnie also missed training after taking a knock in Tuesday's FA Youth Cup defeat against Millwall.
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