Hayden Mullins is expected to shake off injury in time for Saturday’s trip to in-form Burnley.
The Blues midfielder had to be substituted midway through the second half of Saturday’s 2-1 win over Coventry with an ankle problem.
But Pompey boss Michael Appleton revealed the former West Ham midfielder had been replaced by the fit-again Luke Varney only as a precaution.
Appleton explained: ‘Hayden just rolled his ankle slightly but I don’t think it’s anything too serious.
‘He will have a bit of treatment in the early part of this week but it was pretty much a precaution and I would expect him to be fit for Saturday.’
Mullins has yet to miss a game so far this campaign and sat out just one last season through suspension, while Varney made an unexpected return to the ranks after a speedy recovery from his hamstring strain.
Appleton said: ‘It was quicker than expected to have Luke back.
‘Earlier in the week, I thought he would have no chance for the game and then he decided that he felt great on Friday.
‘He had a conversation with the physios and Steve Allen was prepared to let him join in because he had full range of movement in his hamstring.
‘That was a massive boost for me knowing I had the option of Luke on the bench.
‘And we had to take up that option because Hayden had to come off.’
Appleton is also hopeful skipper Liam Lawrence will be back in contention for the trip to Turf Moor.
Lawrence has missed the past four games with an ankle injury but returned to full training last week.