Gary Roberts is set to complete his anticipated switch to Pompey.
The Blues have agreed an undisclosed transfer fee with Chesterfield to bring the 31-year-old to Fratton Park.
Roberts has been a long-time target for manager Paul Cook, who is eager to be reunited with the midfielder at Pompey.
The sticking point has surrounded reaching a fee with the Spireites for a key performer, with 12 months of his contract remaining.
That barrier has now been hurdled and the ex-Swindon man will undertake a medical ahead of signing a three-year deal.
He will join Enda Stevens in linking up with Pompey this week, with Michael Doyle also nearing a south coast switch as Cook’s recruitment drive gathers pace.
However, another target – Jimmy Ryan –is reportedly closing in on a move to Fleetwood Town.
Chesterfield had been optimistic over persuading the holding midfielder to sign a new deal, but those hopes are now fading.
Regardless, the sealing of the Roberts deal will be a massive coup for the Blues.
The attacking midfielder was the cornerstone of Chesterfield’s success under Cook and has also reached the play-offs with previous clubs Swindon and Huddersfield.
A skilful performer, he operates in the centre of the attacking three in the Pompey boss’ favoured 4-2-3-1 system.
Kyle Bennett and Kal Naismith have also arrived at Fratton Park as Cook continues to overhaul his playing squad.
So far, 11 players have left Pompey during the close season, with Craig Westcarr the most recent departure.