Pompey are assessing the extent of Tareiq Holmes-Dennis’ knee injury.
But Milan Lalkovic is expected to be sidelined for up to three weeks with the ankle ligament damage which kept him out against Rochdale.
Lalkovic was pencilled in to start Saturday’s League One clash, only to sustain his injury in training on Wednesday.
Instead the reshuffle saw Drew Talbot handed the right-back slot, with Gareth Evans moved into midfield.
However, debutant Holmes-Dennis hobbled out of the 2-0 victory in the 39th minute, with Talbot moving across to left-back as a stand-in.
Now the Blues are hoping his absence will not be long.
Kenny Jackett said: ‘Holmes-Dennis had made a bright start and looked like the one who could open things up for us.
‘Then he picked up a knee injury. I haven’t really had any information on it yet, we’ll see how it settles.
‘Lalkovic was actually set to play, but got an injury in training, which happens. We have to train, we have to train hard, that is really important.
‘He got a kick on the ankle on Wednesday and it looks like has an ankle ligament strain. He’ll be out 2-3 weeks.
‘To be fair to Drew at right and left-back, he did a good job, although it was slightly frustrating for me that I hadn’t put Brandon Haunstrup on the bench and had a natural left-back. But you can’t necessarily get everything right.
‘Gareth (Evans) is a variable player that will give you 100 per cent whether he is wide right or in a right-back position.
‘Once they went to 10-men we needed him in the full-back position to be able to drive forward and get out, particularly with losing Tareiq, who is good at that.’