Pompey are set to lose Enda Stevens to Sheffield United.
The News/Sports Mail player of the season is poised to quit Fratton Park this summer upon the expiry of his contract.
Paul Cook is desperate to retain the talented left-back, who has made 99 appearances for the Blues.
However, Pompey are unable to compete with the wage offer on the table for the 26-year-old – nor the lure of Championship football.
It had long been feared the club could lose out on the services of Stevens, who has also earned PFA recognition during the campaign.
Now such concerns are to become a reality as he prepares to depart the south coast for nothing.
And it is League One champions Sheffield United who are swooping as they prepare for a Championship return.
The likelihood of losing one of his star players within days of capturing the League Two title is a massive blow to Cook.
Stevens has been an integral part of the Pompey side and one of the chief assist-makers during a magnificent campaign.
It was his cross which was deflected into his own net by Daniel O’Shaughnessy on Saturday to break the deadlock against Cheltenham.
Cook regards the likeable Irishman as the finest left-back in League One and League Two, while has also tipped him for future Republic of Ireland honours.
Yet with Pompey holding off contract talks until their fate was certain at the culmination of the season, it appears they have now lost him.
Stevens arrived at Fratton Park on a two-year deal in June 2015 following his release by Aston Villa.
He had endured something of a nomadic career in England, with loan spells at Notts County, Doncaster (twice) and Northampton.
The defender also made nine appearances for Villa, six coming as Premier League starts.
However, under Cook’s tutelage, he has developed into an outstanding attacking left-back, inevitably capturing the attention of other clubs.
At a gala dinner on Monday night, he was named Pompey players’ player of the season – for a second successive campaign.
It was just reward for a consistent performer so highly regarded among his title-winning team-mates.
Along with Stevens’ anticipated exit, the Blues are seeking to finalise the futures of a host of other members of their first-team squad.
Cook was today meeting the players in turn to reveal whether they are part of his plans in League One next year.
Skipper Michael Doyle, Gareth Evans, Jack Whatmough and Kyle Bennett are the notable players out of contract.
Stanley Aborah, Noel Hunt and Amine Linganzi are also among the 16 whose deals are expiring.