Pompey find themselves out of the FA Cup at the first-round stage for a second successive season after suffering a 1-0 defeat at Luton on Saturday.
However, Brandon Haunstrup feels the Blues would have advanced into the second stage of the competition in fine style on another day – but for a superb showing from Hatters goalkeeper Marek Stech.
James Collins’ first-half stoppage-time strike fired the League Two outfit into the next round at Kenilworth Road.
Despite having 16 shots on goal, Pompey were unable to find a way past Hatters goalkeeper Stech.
Matt Clarke had a header tipped onto the crossbar in the 59th minute.
Meanwhile, the Luton shot-stopper also produced a brilliant save to deny Ben Close from long range at the death.
Haunstrup – who made his first start since September’s loss to Rotherham – believes Pompey were unfortunate to exit the FA Cup at the first hurdle.
He said: ‘The worst thing is we are creating chances but we’re not getting that luck you need to kick on at the minute.
‘We kept them down to chances in first half and then the game opened up a bit in the second period.
‘We were unfortunate not to keep that clean sheet before the break.
‘If we did that, then the game can go either way in the second period.
‘Obviously, looking at the way we played, you’d have fancied our chances in the second half.
‘On another day, you see our chances go in and their goalkeeper does not make as many saves as he did.
‘I’ve seen Ben Close score a lot of those outside the box for the academy – he was unlucky with his effort at the end.
‘He was probably off celebrating before because it looked like it was going in from my point of view.
‘We felt like we were building a good atmosphere – the away fans behind us were unbelievable as per usual.
‘Their keeper has kept Luton in it in the second half.’
Saturday’s defeat had mirror-like similarities to Pompey’s previous game.
The Blues suffered a 1-0 League One loss to Bradford at Fratton Park.
Jackett’s men were punished for a number of missed chances and a defensive lapse condemned to an undeserved defeat.
Haunstrup insisted it is crucial the Blues stop conceding sloppy goals.
The academy product believes if the Blues eradicate those errors then they will quickly get back to winning ways.
‘Our last two games have been 1-0 defeats and it’s just unfortunate, I’d say,’ Haunstrup added.
‘Even against Bradford we had a few chances but just conceded a sloppy goal.
‘We just need to try to contain our opponents and keep their goals goal.
‘If we go into half-time with a clean sheet then we would fancy our chances to then go on and win the game.
‘We’ve now got to go back to the training ground and work on different things, work on being better.
‘We need to stop conceding fewer goals and if we do that then I think we’ll be alright.’