The 29-year-old is expected to join on loan until the end of the season from Saudi Arabian outfit Al-Hilal and if all goes well the Senegalese born player will sign a permanent deal in the summer.
When the central defender completes his move to the Stadium of Light it could lead to Titus Bramble being allowed to move on with QPR said to be keen on landing him.
O’Neill said: “I’m not so sure that anything has been absolutely settled, but if it is, it would be a loan until the end of the season.
“We’re hoping that something might materialise, but there’s a distance to go yet.”
Chelsea will be hoping to brush off their mid-week Champions League disappointment and continue their recent domination of Leicester City when they travel to the King Power Stadium for an FA Cup quarter-final on Sunday.
Charlton have a host of injury absentees as they look to get their League One promotion bid back on track at home to Fleetwood.
Gary Rowett's injury crisis shows no sign of easing as Derby prepare to play host to Championship promotion hopefuls Cardiff.
It's 15th vs 18th at the John Smith's Stadium on Saturday, as Huddersfield and Crystal Palace meet in a crucial battle at the bottom.