Pompey manager Paul Cook cursed the return of the ‘Achilles heel’ which saw them fall flat at Doncaster.
The Blues last night slipped to a 3-1 loss at the Keepmoat to cast doubt over their promotion credentials.
Darren Ferguson’s League Two leaders took advantage of a slack start by Pompey to take the lead through John Marquis before Kal Naismith levelled approaching half-time.
After the break, the visitors were a shadow of themselves as Tommy Rowe and Marquis’ second of the match ensured Rovers strengthened their grip at the summit.
Pompey have a frustrating penchant for conceding first in matches following poor starts.
And it is a recurring problem Cook is desperate to solve – having once more suffered from such an ailment.
Pompey’s boss said: ‘I’m as disappointed as I have been for a long time.
‘What we can’t do is give them the first goal, that’s the reality.
‘There has been Luton away, Plymouth away, and other games when we have conceded goals early on.
‘We have that within us and it’s unfortunate.
‘My job as manager is to keep working to eradicate them and build a team we all want.
‘However, goals change games and we have that ability to give the opposition that momentum to keep going.
‘It’s an Achilles heel. We do the same things.
‘People have got to remember we started at Grimsby so aggressively and strong and, in the first few minutes, Michael Smith had a one-v-one. Last night all we want to do is pass at the back.
‘It is the same lads who make those decisions and all I can keep doing is banging the drum to them.
‘We recovered from that, we always will, we will always get back in, the lads are never shy.
‘What we are is naive. We make mistakes in possession, we just don’t manage to do the right thing at the right time on occasions.
‘And if you give it away in the middle third against a team who just want to break on you then you are in trouble.’
Heading to the Keepmoat, Pompey had recorded four clean sheets in their last five outings.
But old problems refuse to be buried.
Cook added: ‘Coming off the pitch against Luton we were lauding how good our back four are, two or three days later we concede three.
‘We have to stay with these lads and keep working.
‘Football is about habits and our inconsistency sometimes is within our habits.
‘I have got to make sure our habits become stronger.
‘Coming in at half-time, for any neutral we were the better team, we were controlling the game, we looked more of a threat.
‘Unfortunately, the goals then left us on the seat of our pants.’