The 25-year-old left Victoria Park on crutches wearing a knee brace and boss Jim Bentley told the club’s official website: “I feel sorry for Peter and I feel sorry for the group because he’s a big player for us.
“Hopefully after he has a scan the injury isn’t as bad as first feared but it’s not looking great.”
Defender Adam Dugdale and striker Tom Barkhuizen are doubts after they missed the trip to Hartlepool with ankle and thigh injuries respectively.
Sheffield United’s latest signing David Edgar could make his debut for the club.
The Birmingham defender signed on a season-long loan on Monday and Blades boss Nigel Adkins could be tempted to throw him straight into his starting line-up.
The Blades crashed to a 4-0 opening-day defeat at Gillingham and Adkins may want to make several changes, with summer signing Conor Sammon, teenager Louis Reed and fellow midfielder Stefan Scougall in contention.
Che Adams is hoping to retain his place in the starting XI after making his debut for the club in the competition last December when the Blades beat Southampton 1-0 before going on to lose to Tottenham in the semi-finals.