Emiliano Martinez has been left out of the Aston Villa squad to face Crystal Palace amid interest from Manchester United.
There is a possibility of United winger Jadon Sancho being included as part of the deal.
United and Villa also both have interest in Antwerp goalkeeper Senne Lammens.
Sancho is being floated in the talks as the two clubs try to find a solution on valuations.
United have also made an improved offer for Lammens.
