Peterborough United will be without first-choice centre-halves Jack Baldwin and Gabby Zakuani for about a month.
Zakuani suffered a calf injury, while Baldwin damaged medial knee ligaments during Saturday's 1-0 win at Rochdale.
"We've had a bit of bad luck on the injury front," boss Darren Ferguson told BBC Radio Cambridgeshire after Tuesday's 1-0 League Cup loss to Portsmouth.
"It's disappointing to lose my first-choice centre-halves after one game."
Michael Bostwick and 19-year-old defender Ricardo Santos took up the centre-half positions at Fratton Park.
Ferguson may look to bring in cover this week before the visit of local rivals MK Dons.
"First and foremost I have to look at what I've got," he said.
"I'll have a chat with my chairman. There are one or two things we're looking at and we're hopeful we can get one or two in by Saturday."