Oldham will not be distracted by their FA Cup heroics, according to Guy Whittingham.
The Latics face a fifth-round replay at Everton on Tuesday having already despatched Liverpool in the fourth round.
But with stand-in manager Tony Philliskirk recently replacing Paul Dickov at Oldham because of the club’s ongoing relegation worries, Whittingham is anticipating no favours towards his Pompey side.
The caretaker Blues boss said: ‘They have done unbelievably well to get where they are in the FA Cup with the teams they have faced.
‘Why can’t they go to Everton and do the same?
‘But I think they see their League One survival as the key.
‘This is a huge game for them. It’s vital they keep their recent streak going.
‘I think their results have shown that the FA Cup has really spurred them on. But I think they will put out the best team they can tomorrow because the manager will see it is vital to get three points.
‘The Oldham players will think if the play well against us, who is to say they won’t play against Everton?
‘So it’s all on them to play well.’
While Pompey are looking for their first victory in 22 attempts, Whittingham has been encouraged by their recent improvement.
He said: ‘We are looking a lot harder to beat.
‘We haven’t got it right going forward yet.
‘But the priority is that we make sure we are solid, first of all.
‘That’s the dilemma for every coaching team. How much do you take away that defensive solidity and be more positive going forward?
‘We’ve done some work on the training pitch and shown what we think we should be doing in attack.
‘Hopefully, we can be a bit more positive going forward.’