The talented midfielder was not in the squad for the match against Wycombe in League One on Saturday.
That sparked speculation he could be on his way to the Blues who have been active in bringing in reinforcements this January.
But Coughlan insists that if it is in his hands, he won’t allow the player to leave.
He also explained the reason for his absence.
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Coughlan told Bristol Live: ‘Liam Sercombe had a medical problem, that’s the reason he didn’t play.
‘If a club wanted to take Liam Sercombe, I wouldn't allow it. If someone wants to offer silly money... I personally wouldn't allow Liam Sercombe to go anywhere.
‘You could see that we missed him – he's a big player at this football club and if we're to stand any chance we need that type of player.’
The boss added: ‘I got the phone call on Thursday evening, it was a big blow, he's got a problem with his eye.
‘He doesn't look too healthy or too pretty at the moment in time.’
Pompey have already signed Bryn Morris and Andy Cannon during the January window.
The Blues have suffered defeats to Blackpool and now Oxford.