Sean Raggett was recruited as a first-team player, Kenny Jackett has reiterated.
And Pompey’s boss has urged the Norwich loanee not to lose heart following the latest selection setback.
Raggett was not named in the Blues’ 18-man squad for Burton’s visit on Tuesday night.
Despite last weekend lining up against parent club Norwich in the Leasing.com Trophy, he was subsequently omitted from those on duty 72 hours later.
Instead, Oli Hawkins was among the substitutes for the 2-2 draw as Jackett seeks to utilise him as a defender.
For Raggett, it represents more disappointment as he struggles to establish himself during a season-long arrangement.
Jackett said: ‘Sean has to keep working away, his chance with come again, definitely.
‘At the moment we have gone for other options, things will come around for him again.
‘He was seen as a first-team signing, definitely, he came in as an experienced player as well.
‘Maybe he had just come off the back of not having played a in little while, so you have to perhaps be a little patient.
‘He was obviously brought in to affect the first team, there’s no doubt about that, and for him going out of the side now he has to keep working hard and wait for his time to come again.
‘He must wait for his opportunity – then he is capable of being ready to take that chance.
‘Football changes very, very quickly and, in terms of performance level, he is good enough to come through this.
‘I just think he has maybe been a little rusty having not played for a while.
‘Nothing against Sean at all, my choice has, at present, been for Downing and Naylor.’
Raggett’s sole League One start was last month's infamous Fratton Park draw against Coventry.
Jackett added: ‘Oli has obviously had an injury. Coming back into it, he gives us a very good presence in both boxes.
‘For Sean, it is not necessarily people going past him in the pecking order, you have to work hard.
‘Make sure when you get your chance then you must take it – and his chance will come again.’