Ndiaye is in the final year of his contract and Marseille have been pushing to secure a deal to sign him all summer.
The attacker initially agreed to stay on at the newly promoted Premier League side and almost agreed on a new deal with the club.
However, disagreements over a release clause meant Marseille joined the race again and they are now closing in on a deal to sign him this summer.
Ndiaye is due to play a friendly against Rotherham today but behind the scenes, his future is being sorted out away from Bramall Lane.
Marseille are pressing forward with an attempt to get a deal over the line in the next 24 hours.
Sheffield United are also now resigning to losing Ndiaye this summer and will now look to spend the cash on a replacement.
The French giants are expecting to agree on a deal worth £15m for the signature of the Senegal international.
A former Marseille academy product, Ndiaye has been keen to return to his former club and has already agreed personal terms with the French giants.
Everton have also been interested in him but Marseille are closing on securing the attacker’s signature.
