Fulham are finalising a deal to re-sign defender Terence Kongolo from Huddersfield.
Manager Scott Parker has been keen to strengthen his defence following a poor start to life back in the Premier League.
Defenders Tosin Adarabioyo and Joachim Andersen joined Fulham on Deadline Day from Manchester City and Lyon respectively.
But Parker has moved once again to bolster his options, with announcement on Kongolo's arrival expected in the next 24 hours.
The 26-year-old joined Fulham on loan in January, but suffered a broken foot and returned to Huddersfield after making just one appearance for the Cottagers.
Kongolo began his career in his native Netherlands with Feyenoord and made over 130 appearances for the club before moving to Monaco and then to Huddersfield.
He made 45 Premier League appearances for Huddersfield during their two-season stint in the top-flight.
Kongolo has been capped at every level for the Netherlands and has made four appearances for the senior team.
West Brom have agreed a fee worth around £15m with Huddersfield for striker Karlan Grant.
Negotiations have been ongoing for more than a month, mainly over the structure of payments, and the two clubs have now reached agreement on that area.
Grant will have his medical at The Hawthorns on Thursday, and Albion will pay the majority of the fee in future instalments.
A domestic transfer window between Premier League and EFL clubs remains open until October 16 - dubbed Deadline Day Two - but how does it work?
The international deadline - where English clubs could buy, sell and loan players from abroad - closed on October 5, but an agreement between Premier League and EFL teams means players can still be transferred in England.
Following consultation between the leagues - and because FIFA allows a summer transfer window to run for up to 12 weeks - Premier League clubs can still do business with EFL sides for a further 11 days in a bid to bolster their squads.
They can make loan or permanent signings, as well as selling, but there cannot be transfers between Premier League teams.
All EFL clubs can still do domestic business with any English team up until Deadline Day Two on Friday.
The domestic transfer window will run until 5pm on Friday, October 16.