Matt Clarke is adamant Pompey can eradicate their defensive lapses.
The centre-back insisted the Blues are working hard to break their bad habit of conceding goals in the early stages of both halves.
Last season Pompey registered the second-best defensive record outside the Premier League as they clinched the League Two title.
Today, Kenny Jackett’s side entertain Bradford, having conceded 19 goals from their 15 games to date in the third tier.
Fourteen of those have come on the road, with five shipped in the recent away defeats to Doncaster and Blackburn.
And the two conceded against Donny – both scored within the opening six minutes – proved costly as they gave the Blues a mountain to climb from the start.
There have also been defensive lapses immediately after half-time, with early strikes contributing to defeats against the likes of Oldham and Oxford.
Clarke revealed Pompey are scrutinising why they have been starting each half slowly.
And they are determined to put a stop to the disturbing trend, starting today against third-placed Bradford (3pm).
‘The way we start games is something we have got to look at – we need to be a bit more solid,’ said Clarke.
‘We’ve been making too many mistakes and poor decisions on the ball, which lead to chances against us.
‘Maybe we give our hands away a bit too early.
‘We have got to make sure we stay in games and stay compact for a bit longer.
‘It’s those moments we are not quite getting right or we’re missing a bit of luck, but it’s something we’re definitely working on and trying to improve.
‘You can’t really put your finger on it, but as a unit we are working on it every day to make sure we don’t go down at the start of games.’
Pompey’s defence has been transformed since they won last season’s League Two title.
Clarke and Christian Burgess remain at centre-back, but have been joined by new defensive team-mates.
Left-back Tareiq Holmes-Dennis was originally brought in to fill the void left by Enda Stevens’ departure. But a long-term knee injury has denied him that chance, with Damien McCory, Brandon Haunstrup and Dion Donohue all acting as cover.
Nathan Thompson has been preferred at right-back to Gareth Evans, yet has been absent for periods through injury.
Meanwhile, keeper Luke McGee has replaced David Forde in goal.
But Clarke, who missed the first six games of the season with a hamstring problem, has not pinned Pompey’s woes on the new-look rearguard.
He added: ‘Whoever plays we try and be solid.
‘It’s rare the whole back four play together all of the time throughout a season because of injuries and other things.
‘We have got to be a unit, regardless of who is playing in the back four.’