Kenny Jackett doesn't believe Pompey's trip to Bradford is a must-win game for his side.
The Blues head to Valley Parade tomorrow night sitting just outside the play-off spots in seventh.
They are one point adrift of sixth-place Plymouth, who have a game in hand, and Scunthorpe, who sit fifth.
Pompey have four games left this season and will occupy the play-off positions with victory against Simon Grayson's struggling Bantams.
A draw won't be good enough given Plymouth and Scunthorpe's superior goal difference.
However, speaking at his pre-match press conference, Blues boss Jackett insisted all won't be lost if his side fail to get the three points in West Yorkshire.
'I don't think that will be the case,' said Jackett, when asked whether defeat against Bradford would make it hard for Pompey to reach the play-offs.
'I think it will be open for us on Saturday (against Charlton).
'We'll need to win all three games perhaps - but that's possible. You can win three games of football, and we've proved that this season.
'I don't think, in terms of a club in this division, we'll ever be far away from putting the type of run together and performances together that can happen around those play-off places, that's our aim and that's where we want to be.
'Our job is to work hard, build and improve the team all of the time with a view of getting into the Championship
'Whatever happens on Tuesday, it will still be open for us on Saturday.
'But we have to see the opportunity, try to take it, and if we win on Tuesday the atmosphere will be fantastic at home to Chalrton on Saturday.'