River Plate are watching closely Enzo Fernandez's situation at Benfica.
Manchester United and Chelsea are considering meeting the Argentina World Cup winner's €127m buyout clause.
And should the option be triggered, River will be due a stunning windfall.
Selling Fernandez to Benfica in the summer, River secured a 25 per cent sell-on clause as part of the €16m deal.
As such, should the midfielder leave for his clause, River will be due €31.75m from the sale.