Hayden Mullins is poised to leave Pompey within the next 24 hours.
Michael Appleton believes Reading are close to capturing the midfielder on loan until the end of the season.
Mullins was left out of the Blues squad against Brighton at the weekend following interest from his home-town club.
However, he has this week continued to train with Pompey while talks have continued.
Any prospective deal would be with a view to a permanent move in the summer.
And Appleton is looking for it to be concluded soon.
He said: ‘I think it will happen, we are just at a point where both sides are talking.
‘It could even happen in the next 24 hours.
‘Hayden has still trained with us, there are no problems there.
‘The reason he didn’t feature against Brighton was because I didn’t want anyone in the process of leaving playing for the club.
‘I want players with a clear mind and focused on playing for us.
‘I am not saying Hayden would not get on with his job, he has played every game under me.
‘But I cannot put players in there who are not going to be here for the next game. I need to look beyond that.’
Mullins has made 128 appearances and scored three goals since joining in January 2009.
Meanwhile, Appleton has dismissed reports of loan interest in Danny Ings.
The 19-year-old joined Burnley in August, but has been sidelined with a cruciate injury before recently returning.
He added: ‘That is the first I have heard of that.
‘I have no idea where that has come from. It is certainly nothing to do with me.
‘The lad is a decent player, but not one who has come up in the conversations I’ve had.’