Josh Thompson’s potential Pompey arrival has been put on hold over problems with the length of his loan.
The central defender has spent the past three weeks training with Michael Appleton’s squad.
During that time he has started two pre-season friendlies and appeared as a substitute against Aldershot.
Currently still contracted to Celtic, Pompey had been weighing up bringing Thompson in on loan.
However, Scottish Football Association rules stipulate that there can be no short-term loans between clubs in Scotland and England.
Instead, any deal must be from window-to-window.
And with the Blues unable to sign players for more than a month at present, it means the switch cannot move forward.
Appleton said: ‘We are just not in a position to do it at the minute. We are only allowed to do month-to-months (deals) and because of the cross-border rules that doesn’t allow you to do that.
‘It is only allowed to be from window-to-window so I am not sure the Football League would allow it.
‘We are sort of still monitoring that one and Josh is still here. What happens next is his call and what he wants to do.
‘Theoretically, he could still sign for us. But, firstly, we would have to find the money and, secondly, he would have to give up his contract at Celtic.
‘I am not sure if he would be comfortable enough to do that.’
Meanwhile, former Stoke midfielder Tom Soares remains on trial as he seeks to impress.
Appleton added: ‘Tom is still here training.
‘In fairness, he is probably training in the hope sometime soon we may able to do something more with the players.’