Big deals are unlikely for Kenny Jackett’s men with the salary cap and restrictions working against them, but there could still be a late deal or two in the pipeline.
Pompey will also be keeping a close eye on what their promotion rivals are doing today too, with League One expected to see a number of loan moves.
Sunderland are unlikely to do much business on incomings today, having completed the signing of Ross Stewart last night from Ross County.
However, Stewart’s arrival should be the trigger for Sunderland to let Grigg leave. The 29-year-old has been a huge disappointment since his high-profile move two years ago, and there are a host of League One sides interested in taking him, including Oxford United and Shrewsbury Town.
Johnson added: "Will wants to play every game, he wants to be closer to his family who are in Stafford, and we are probably going to have to accommodate that on this occasion if we get that extra man in."
Shrewsbury could be one of the busiest League One teams today, as they look to add three or four players to their ranks before the window shuts, similar to Oxford.
At the top end of the division, Peterborough United are hoping to hang on to their star striker, while Doncaster Rovers’ business has all but been done – though they are braced just in case they get a bid for one of their main defenders from Preston.
Hull City could be set for a quiet day with the promotion favourites having already completed a lot of their business, though Gillingham boss Steve Evans – no stranger to a transfer or two – is hoping to get a number of players in to bolster his squad.
It promises to be a busy end to the window, which shuts at 11pm. Here’s a list of some of the big deals that could go through in League One before the deadline.
1. Joe Wright
Doncaster Rovers defender Joe Wright has been linked with Preston after they accepted a £2million bid for Ben Davies from Liverpool. Rovers will be keen to keep hold of Wright, while Preston have other options. Photo: Julian Finney
2. Tom Pearce
Wigan Athletic's Tom Pearce is interesting Sheffield Wednesday, though the financial state of both clubs may mean a deal is tricky to get done. One to keep an eye on. Photo: Michael Regan
3. Josh Tymon
Stoke City left-back Josh Tymon is on Shrewsbury Town's watchlist as they look to add a defender to their squad. A loan deal could go through today. Photo: Nathan Stirk
4. Elliott Bennett
Shrewsbury Town are keen on bringing Blackburn club captain Elliott Bennett back to Shropshire. Bennett, out of contract at the end of the season, worked under Steve Cotterill at Bristol City and would be an option in midfield and at right wing-back. Photo: Lewis Storey