Guy Whittingham fears other players could follow Lubomir Michalik after the defender became the latest to quit Fratton Park.
The 29-year-old Slovakian has informed the club he will not be renewing his deal when it expires tomorrow, with a move abroad lined up.
He joins Izale McLeod in turning down the chance to remain with the Blues on another one-month deal during administration.
Whittingham last week released Brian Howard, Lee Williamson, Mustapha Dumbuya and Jon Harley after being put under pressure by administrators PKF to cut costs.
The caretaker boss wants to retain the remainder of his Pompey squad, which currently numbers just 13.
However, the deals for Simon Eastwood, Johnny Ertl, Darel Russell, Liam Walker and Ricardo Rocha are also up this month.
And he is concerned they may also elect to walk away when their contracts run out.
‘Lubo told us towards the end of last week he is going to leave,’ said Whittingham.
‘It’s that unique situation we are in – and unfortunately it happened with Izale.
‘Okay it might have been our decision with the other ones but I am sure one or two of them had thought about leaving anyway and Lubo has done the same.
‘You can understand the reasons because unfortunately we are in the position we are in and we just need to get this sorted.
‘Nobody else has said they are going, not at the moment – but you try to put yourself in a player’s situation.
‘They are on a month-to-month but if they get an offer to take them until the end of the season or to go and sign permanently for 18 months or two years somewhere else, what would you do?
‘We’re in difficult circumstances, it has to be said.
‘There is nothing we can do about it.’
An exodus of players during the January transfer window had long been expected.
It is down to the ownership situation not being resolved.
And Whittingham says the latest crisis has never before been witnessed.
He added: ‘People can say the players are on month-to-months and it got them to January – but it is not only that.
‘There wasn’t a decent pre-season here and it’s vital you get off to a good start.
‘We weren’t able to do that because of the different players coming in.
‘Even the first game at Plymouth we had to play all the youngsters and it has just been an incredible situation I haven’t heard of in football before.
‘I’m not harping on about it to get sympathy, I’m just saying it is the uniqueness of the situation we are in.
‘Every football club has their problems, everybody has different problems on different scales but I just think this is more unique.’