Any fears have been allayed, though, with Clark Robertson finally becoming the Blues’ first senior signing of the summer.
Granted, Liam Vincent was the first to move to Fratton Park earlier this month from Bromley.
The teenager’s arrival’s been welcomed on the whole as tangible evidence of an investment for future years.
But supporters ultimately craved an established Football League player who’s very much for the here and now. They’ve got that in Robertson.
The Scot was heavily linked throughout the summer and it’s scarcely a surprise other suitors were rivalling Pompey after his departure from Rotherham.
Yet Cowley got his man, ensuring he addressed the spine of the team he’s made a priority in the early stages of the window.
In addition, it underlines how the head coach wants to mould his defence - comfortable and adept at playing through the thirds.
Robertson was described as arguably the best ball-playing centre-back in the third tier by Gary Bowyer when at Blackpool, such is his prowess in possession.
Given he's a left-footer, all things suggest he's been brought in to be at the fulcrum of Pompey's rearguard.
That will, therefore, mean him filling a berth at someone else's expense.
And, as things stand, the likeliest candidate who will be usurped is Sean Raggett
After all, it's his role on the left-hand side of the rearguard that Robertson has arrived on the south coast to take up.
Raggett's proven a worthy servant during his two years at Pompey. In his 90 appearances, no-one can deny he's always given his all.
Not once has he shirked an injury-threatening challenge or a header that ran a high risk of concussion. He is simply fearless, while he's always a threat from set-pieces.
However, the final game of the 2020-21 season was perhaps a stark insight into where Raggett would rank in Cowley's plans for the upcoming campaign.
Despite starting all 45 league matches before Accrington visited Fratton Park, the ex-Norwich man found himself demoted to the substitutes' bench.
Jack Whatmough was restored to the starting XI despite serving a five-match suspension, while Paul Downing kept his place for just a third league appearance of the campaign.
A blow for Raggett, no doubt, who understandably would have felt aggrieved to have lost his spot for the more important game of the term as Pompey chased the final play-off spot.
Even more so was it a surprise because he's a player who's previously worked under Cowley at Lincoln. He earned a move to the Championship after helping the Imps to the National League title in 2017.
However, Cowley's footballing style has adapted since. His Lincoln side was very much direct given the players he inherited.
Since Cowley's moved further up the pyramid, though, and evolved his coaching philosophy, it's become more expansive.
In the 12 games the head coach was in charge of at interim boss at PO4, it was evident he sought to implement an approach that involved playing out from the back.
That meant there were concerns if some of the personnel that had been passed down by predecessor Kenny Jackett were capable of doing so. Raggett was among them.
There is the possibility to switch Raggett to the right-hand side and play alongside Robertson. They did indeed partner each other at Rotherham on occasions in 2018-19.
In theory, it should be Raggett’s natural position. Yet he never looked quite comfortable there when next to Rasmus Nicolaisen last term, having played on the opposite side for the vast majority of his career.
Then factor in how Downing was praised highly by Cowley after his return from the cold. It suggests he might finally get a sustained run in the team after spending the previous two years surplus to requirements.
Being on the Pompey periphery is a position Raggett’s rarely found himself in.
It would be folly to think Cowley wants to offload such an established League One performer now he has Robertson.
But the ex-Aberdeen man’s arrival means, barring any injuries, Raggett may start the upcoming season in the same place he ended the last – as back-up.