Jack Whatmough has sprinted ahead in the race to partner Christian Burgess in the heart of Pompey’s defence.
But Tom Davies is focusing on closing the gap as he makes a late surge for first-team football following injury.
It has been frustrating not being able to show what you can do on the pitch. I have to get to the level the other defenders are out, which is something I am willing to doTom Davies
A 12-minute cameo against Bournemouth on Saturday marked the summer recruit’s second appearance of the pre-season.
A back spasm sustained while training in Ireland sidelined the centre-half for four of the Blues’ summer friendlies.
In his absence, a resurgent Whatmough has staked a strong claim to line up against Carlisle for League Two’s August 6 kick-off.
The list of rivals for the centre of defence have already been reduced through Matt Clarke’s on-going groin issue.
Adam Barton is also in the running, with Burgess unquestionably a dead cert to take up one of the central spots.
Paul Cook’s side travel to Bognor tonight (7.15pm) for their latest outing, with Davies expected to feature against the non-leaguers.
And he is eyeing enhancing his claims for a first-team role as he plays catch-up.
Davies said: ‘The injury was a frustrating one, it was meant to keep me out for a couple of days but tightened up a bit more.
‘Although I was desperate to train, I had to sit out 10 days.
‘These things happen, it’s pre-season so you are going to get niggles and that, but it is out of my mind now and hopefully I can kick on.
‘I am back training with the lads every day, getting my fitness up to where it should be, while maybe doing a bit of extra work when the lads have finished training.
‘It has been frustrating not being able to show what you can do on the pitch. I have to get to the level the other defenders are at, which is something I am willing to do.
‘Jack has done really well, no doubt about that, he has been excellent and that is something I have to aspire to.
‘Hopefully if I can keep working hard and training hard, showing what I can do, then I can give the gaffer a problem.
‘Once everyone is fit there are five to pick from so I’ve got to come into the gaffer’s thoughts when he is selecting the team during the season.
‘I just want to get games under my belt and give the gaffer a problem because the lads playing centre-half at the moment are doing really well.
‘It’s not just me trying to impress, though, it is the same for everyone else in the squad.’
Certainly, Clarke would have been at the forefront of Cook’s mind when planning ahead to this season.
But the 19-year-old has not trained since collecting his groin injury in April and continues to be ruled out of this season’s early stages.
Davies added: ‘Matt is a great player, and will hopefully be coming back when his groin is sorted.
‘That’s the thing, you are not going to win leagues if you haven’t got good players in reserve as well.
‘So the central defenders will push each other hard and, hopefully, it will work well for the team.’