The Blues’ chief executive explained that American owner Michael Eisner made more money available to Danny Cowley after the contracted players who remained following a close-season overhaul took up two thirds of the money originally made available.
Pompey’s boss oversaw a huge turnaround in the club’s first-team set-up, with 10 senior players allowed to leave either on free transfers – or in the case of James Bolton, for an undisclosed fee.
A host of youngsters who had gained senior experience under previous boss Kenny Jackett were also allowed to depart.
Meaning 14 replacements had to be found before the transfer window closed on August 31 for Cowley to put his stamp on the side he inherited.
But Cullen admitted additional costs were incurred along the way – particularly in the deals that saw Joe Morrell, Miguel Azeez and Mahlon Romeo arrive on the south coast.
And it was an overspend that was sanctioned by Eisner.
Speaking about the ‘decent budget’ Cowley went into the summer with, the Blues CEO told the club’s website during his latest Q&A: ‘In terms of our transfer budget, we actually overspent in the summer.
‘We paid money for Joe Morrell later in the transfer window where our owners sanctioned an overspend on the budget.
‘In terms of wages, we also overspent our budget by acquiring Miguel Azeez and Mahlon Romeo on loan, and there were situations where we asked our owners for a little bit more and they were happy to support Danny and myself in terms of doing that.
‘We had a decent budget and we also had a particular challenge in the summer where two thirds of our playing squad were out of contract and we had two thirds of the budget committed to the one third that were left over.
‘We had to be smart in the way that we recruited.’
Speaking on the business Cowley did, Cullen admitted experienced players who could immediately fit into the head coach’s playing philosophy were head hunted.
Six of those signings started Saturday’s 4-0 victory against Sunderland as Pompey ended a seven-match league run without a win.
But the Blues chief admitted younger players would be the focus in future windows.
He added: ‘We had some big names to replace and I think we brought some really good players into the building, and I think it’s a matter of time until it starts to click properly.
‘We’ve got to be patient, and patience is not really something that you have in football, and I fully understand that.
‘We’ll start to see progress over the next few windows because this summer it was important to get some experience into the squad that can cope with the adaptation and the style of play Danny wants to implement.
‘Down the line I think we’ll look to bring some young talented assets into the building that are good enough to play for the first team, grow and develop, and help the club reach its aspirations.’