The Blues slumped to 3-1 defeat at Blackpool last night following an awful defensive performance.
Individual errors were responsible for a concerning third league defeat on their travels this season.
Conor Chaplin’s spectacular overhead kick represented the only positive for the 737 travelling fans gathered inside a sparse Bloomfield Road.
Pompey remain a force at Fratton Park and entertain third-placed Doncaster next weekend.
However, they have now won just once away from home this term – and Cook is desperate to find a solution.
He said: ‘In this game it is all about being as good as you can be and what we have proven is we are good – but, unfortunately, we have something in us which isn’t good.
‘Does that mean we have to try to change stuff away from home? I think we have to because what we have seen is not good enough away from home.
‘Everything that was good about us Saturday and good about us at home becomes disappointing away from Fratton Park.
‘You probably go back to years when Portsmouth didn’t travel well – and we are now looking like that team.
‘We just look soft, we look like if you put balls into our box we’ll concede, it’s really disappointing, it was one of those nights.
‘The reality is the same players took to the pitch last night who put in that performance on Saturday which gave the club so much pride.
‘Yet last night was the complete opposite.
‘We started making mistakes and decisions in the game that you couldn’t believe.
‘I have watched it from the sidelines enough to know that is in us – and that’s the disappointing thing.
‘Blackpool felt there was something there for them and you could see why, because our play was generally sloppy and untidy, it wasn’t crisp.’
The Blues have collected four points from a possible 15 away from Fratton Park this season.
In contrast, they have four victories and a draw on home turf.
The manner of their latest defeat also worried, with players caught in possession being responsible for two of Blackpool’s goals last night.
And that recklessness from the fourth-placed side infuriated the manager.
Cook added: ‘For 15 minutes we did excellent and had a couple of good situations – then gave Blackpool the first goal which lifted them.
‘After that, the goal after half-time is just scandalous – that’s football, though.
‘If you want to give somebody confidence, just play on the edge of your box and pass the ball in. We got tired and weren’t bright with our play, we weren’t penetrative with our passing.’