The Blues have been forced to admit defeat in their pursuit of Jake Jervis.
And Pompey will now step up the chase to find an alternative striker before the emergency loan window closes today.
Jervis has failed to be given international clearance by Fifa and has now stopped training with the Blues.
The rejection hinges on the fact the 22-year-old was still contracted to Elazigspor on the final day of the September 3 transfer window.
It means the striker is not recognised as a free agent by Fifa and cannot sign for a new club until January.
Fifa’s findings contrast with the claim of Jervis and his agent, who had told Pompey he was a free agent having had his contract cancelled by mutual consent this summer.
Gavin Mahon has also left the club after three appearances, with his short-term contract scheduled to expire in a week’s time.
Yet it is understood the Blues are searching for another striker ahead of today’s 5pm deadline to bolster the side for Saturday’s trip to Hartlepool.
Catlin said: ‘Jake Jervis is over, his international clearance has been rejected.
‘It’s for the reason that on September 3 – transfer deadline day – he was still a registered player in Turkey. So Fifa got to the bottom of that.
‘Jake and his agent say his contract is up because he served notice on them but if you speak to the Turkish federation he was still registered on September 3 and cannot go anywhere until January.
‘There’s nothing we can do, Jake has been great in training and we have looked after him but ultimately, at this minute in time, Andy (Awford) has got to concentrate on the players that are here for the next three games.’