Michael Appleton is hopeful Luke Varney will be fit for the south-coast derby.
Pompey’s top scorer limped out of the action after 20 minutes of Saturday’s victory at Burnley.
He injured his knee during a mid-air collision with Clarets keeper Lee Grant.
It was Varney’s first start since recovering from a hamstring injury sustained in Appleton’s opening match in charge at Watford.
With the knee swollen, Pompey’s medical team will reassess the problem today.
And Appleton is keeping his fingers crossed the former Derby man will be available for the eagerly-anticipated visit of Southampton next weekend.
He said: ‘It is not Luke’s hamstring – he’s got a bang to his knee.
‘As he lifted the ball over Grant he caught his knee so it is more of an impact injury.
‘It’s a little bit sore at the minute and a bit stiff.
‘He’s had a little bit of ice and we are hoping it will settle down and we will see how bad it is.
‘Today we will have an idea of where we are with him, so we will have to reassess him after that.’
A free-kick was given against Varney in that 16th-minute Grant clash.
Referee Steve Rushton adjudged the forward’s foot to be dangerously high so penalised him as a result.
And Appleton admitted he was ‘baffled’ by that decision.
He added: ‘It was really disappointing to lose Luke on Saturday.
‘I thought he looked really sharp. He looked a real threat early doors and I thought caused them all sorts of problems.
‘It was a shame to lose him and an absolute baffling decision but you have got to move on.’