That is the reality check delivered by Michael Appleton to dash any hopes of the up-for-grabs pair coming back to Fratton Park.
Mattock is a free agent having been released by West Brom.
The former England under-21 left-back impressed during seven matches on loan at Fratton Park before being recalled by the Baggies at the turn of the year.
Meanwhile, Derby have put Maguire up for sale as Nigel Clough seeks to raise funds for a summer recruitment drive.
The Scottish striker made a massive impact during his emergency loan spell at Pompey, scoring three times and finishing the campaign as the outstanding performer.
But despite both players being available, Appleton has ruled out them coming back.
Instead, the Pompey boss will continue to work within his budget at a time the club remains without owners and with a registration embargo still enforced.
Appleton would love for both to return – but admits he is forced to look elsewhere to meet the 18-player target he has set himself to recruit during the close season.
He said: ‘You have to be realistic about this and we have a budget which I am sticking to.
‘Joe Mattock is free and I have spoken to his agent and asked to be kept in the loop.
‘Realistically, though, it is not going to happen and we must accept that. We just cannot afford him so I’m looking elsewhere.
‘I would imagine there would be offers from the Championship for Joe and I would imagine the wages he wants would probably be a little bit too steep for us.
‘I have been told there are two or three clubs who have enquired about him, and with the budgets they have, you cannot compete with that.
‘It’s a similar situation with Chris, who obviously also did really well for us after coming here on loan. Derby are going to want a decent chunk of what they paid for him just a year ago, which again is too much for us.
‘We can’t afford to pay transfer fees.
‘That is just the way it is. We have to be realistic about what we can and cannot do this summer in terms of bringing players in.’
Mattock caught the eye during his Fratton Park loan spell following a steady start. Appleton wanted him back for a second loan spell after Christmas, yet Pompey’s finances meant the plug had to be pulled.
Instead, the ex-Leicester full-back spent the second half of the season at Brighton.
As for Maguire, he spent the final two months of the campaign on loan at Fratton. The former Aberdeen forward scored three times in 10 outings, including a stunner against Southampton.