And Rasmus Nicolaisen has been urged to keep on battling as he attempts to find a way past.
Jackett has opted for a central-defensive axis of Raggett and Jack Whatmough in all seven League One games this season.
Last night the Blues responded with a third league clean sheet as they claimed an impressive 2-0 success at Gillingham.
In his 50th Pompey outing, Raggett was imperious in the air, putting in arguably his finest display of the campaign so far.
And while Nicolaisen is breathing down his neck for the left-sided centre-half role, Jackett has backed the former Norwich man to retain his spot – for now.
He told The News: ‘Sean was outstanding last night, he is a big player for us and will gain in confidence.
‘The more he plays, the better he is.
‘He did well last season and he builds into it. He was a big player for us last year and is a very, very committed character.
‘One or two people have said to me that it takes time for him to get going at the beginning of the season – maybe it does everybody. You need to get into a rhythm.
‘But it will go the other way where we have so many games now and I think it will be good for us.
‘I have been pleased with Sean and Jack so far this season.
‘Rasmus has done well too, he has to keep his head up and his chance will come.
‘There may be days when you play a three, but, similarly, we have spun the formation a little and I want to try to settle it down if we can.
Nicolaisen, who is on a season-long loan, has made two appearances so far and was once again an unused substitute last night.