Kenny Jackett insists League One remains open for Pompey to propel themselves up the table.
And the boss believes it's only Ipswich who've got things spot on so far this term.
The Blues delivered just a second victory in the league against Bolton last Saturday.
It arrived after a run of five games without a third-tier success and on the back of an abject 1-0 loss at Wycombe the previous weekend.
Pompey's stuttering start means they sit 19th, although they have played three games fewer than others.
What’s more, Jackett’s men are 10 points off the play-off places – but that deficit would be reduced to just one point should they win all their matches in hand.
The Fratton Park manager is certain, however, there’s ample time for the Blues to find the momentum to climb the standings.
Jackett said: ‘It has been a tough start but we have got to believe we can find momentum – big clubs can.
‘We have got to believe we can find momentum and consistent wins to climb the table.
‘We haven’t played well. If you’re looking at Wycombe, we just didn’t play well.
‘Any criticism that is coming my way, we have to accept because we didn’t play well at Wycombe.
‘It was a 50/50 game, a penalty decision and we have to perform better than that to be able to get a run of results and build momentum and confidence.
‘We are capable of it and earning that as long as we are honest with each other.
‘We are capable of going on a run because there is a lot of the season left.’
Ipswich are top of the table, having won seven and drawn three of their 10 fixtures to date.
Wycombe (22 points) are second, with Coventry (20), Fleetwood (20), Sunderland (19) and Blackpool (19) occupying the play-off spots.
From the outside looking in, Jackett feels it’s only the Tractor Boys who have convincingly demonstrated they’re promotion contenders.
He added: ‘It seems it (Ipswich have got it right) from afar. We haven’t played everybody and it’s not a criticism on anyone in the division.
‘It’s just an observation that Portsmouth can still be competing at the top end.’