But as we wait for number 23 to arrive, with Josh Griffiths edging closer to a Fratton Park switch, we’ve decided to take a look back at the players the Blues manager has turned to in a bid to achieve success on the south coast – and offered an opinion on whether they are or have been a hit or a miss.
Here’s the judgement we’ve made, with emergency keeper Jake Eastwood not included given the very brief period he spent on loan from Sheffield United.
5. Connor Ogilvie
The former Gillingham defender arrived at Fratton Park with a decent reputation. His Pompey career got off to a slow start but by the time it ended, the former Spurs youngster was one of Cowley's most reliable performers. Verdict: Hit. Photo: Graham Hunt
6. Clark Robertson
Injury problems over the first half of the season made many question Robertson's presence - especially after Jack Whatmough's departure in the summer. However, since the turn of the year, the centre-back has proven to be a welcome addition to the Pompey ranks and a leader.
Verdict: Hit. Photo: Jason Brown
7. Louis Thompson
Thompson arrived on a free transfer from Norwich with an injury record that overshadowed his undoubted talent. Cowley did his best to manage the midfielder's fitness. And what a job he did as Thompson - who was on a pay-as-you-play deal - racked up 38 appearances in total. As his fitness levels grew, so too did his Pompey presence.
Verdict: Hit. Photo: Joe Pepler
8. Liam Vincent
The youngster was brought in from non-league football with one eye on the future. That remains the case, but his first season at Fratton Park proved a nightmare thanks to a prolonged shin injury. That ruled him out for the vast majority of the campaign. He'll be hoping for better luck this summer, but for now he sits in the 'Miss' section.
Verdict: Miss. Photo: Portsmouth FC