The Bulgarian is training with the Blues after leaving League One rivals Burton Albion.
But Kenny Jackett has denied a move is imminent for Blackburn defender Paul Downing.
Pompey have been linked with Downing, who is available after falling down the defensive pecking order at Ewood Park.
Jackett said: '˜No, we've got Bryn signing on Monday but Paul Downing, no.
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'˜We have Evtimov who played against us for Burton.
'˜He's been in on trial with Luke McGee out injured. He's a free agent.'