Neymar reportedly asked for a clause to be inserted in his Paris Saint-Germain contract that will allow him to leave the club should Kylian Mbappe not sign a new deal of his own.
Brazil international Neymar agreed a four-year contract extension at the Parc des Princes last month, ending months of speculation over his future.
However, fellow forward Mbappe has still yet to commit to a new deal and is due to become a free agent in a year's time.
According to Spanish outlet AS, losing Mbappe to Madrid could prove to be a double blow for the Parisiens as per the agreement in place with Neymar.
However, the report indicates that PSG only agreed to insert the clause in Neymar's deal as they are confident of getting Mbappe to put pen to paper.