Richie Barker admitted the on-going issue over lacklustre Pompey second-half displays remains a worry.
Poor fitness has already been put forward by people outside the club as being behind alarming slumps.
It was another shocking second-half display on Saturday as Bristol Rovers secured a 2-0 win with a goal in each half.
Afterwards Barker was keeping his cards close to his chest over what he believes is the reason for the on-going concern.
Yet it is something he has targeted solving.
He said: ‘A few people said at half-time we were the best team in the first half, but how many times has that been said this year, whether it was me or Guy?
‘I don’t hear many people saying we were the better team in the second half, which is a worry for me.
‘In that first half I thought Jed (Wallace) was fantastic and Patrick (Agyemang) they couldn’t handle.
‘Obviously with a couple of little breaks we could have gone in a goal up, we could have gone in a couple of goals up to be fair.
‘But we didn’t, we are going to keep working until we change it.
‘I have got my own feelings of why it is that the second half is not great, but I will keep it to myself for the time being.’
The result could have been different if Ryan Bird had not spurned a great opportunity in the 26th minute.
Instead from six-yards out keeper Steve Mildenhall blocked his shot with his feet.
It was Pompey’s last attempt on target and proved to be a key moment in the outcome.
Barker added: ‘It was a key moment and there can be key moments both ways.
‘Obviously going a goal up changes peoples’ mentality and attitudes and gives them more belief, which is understandable.
‘Getting the first goal would be important.
‘I don’t know the last time that happened at the football club.
‘There is obviously an issue with that in terms of trying to get the first goal. I don’t know what it is and I’m not going to stop until I do.
‘But if every time we go a goal down and we’re never going to get back in it then it is going to be a long season.
‘You are never going to always score the first goal.’
– NEIL ALLEN