However, Fuller travelled to America for a diagnosis on his knee problem and was told by leading surgeon Dr Richard Steadman that he is clear to carry on playing.
Now Pompey are keen to sign Fuller again but don't fancy paying the estimated £1.5 million fee Preston want for the player.
"It is still possible we could take a chance on Fuller with a pay-as-you-play deal but the drawback is you can never sign him on a full contract with that knee problem," said Pompey boss Harry Redknapp.
"He would never pass a medical and so you could never sell him on."