The Blues midfielder is believed to be on the verge of exiting Stamford Bridge, with discussions between the player and the club imminent.
Mata is thought to have grown frustrated at being overlooked by Jose Mourinho this term, despite having been the West London side’s top performer over the past two campaigns.
This has alerted Real, who are keen to swoop if they lose Di Maria.
The Argentine is similarly frustrated in Madrid, with Gareth Bale’s arrival having diluted his role in Los Blancos’ first-team.
A number of sides are interested in the versatile South American, with a move away from the Spanish capital in the coming weeks possible.
Mata is seen as an ideal replacement, and a player that could link well with Bale, Cristiano Ronaldo and Karim Benzema.
The 25-year-old may be tempted by a return to his homeland ahead of the World Cup, with regular playing time in full glare of the nation’s media likely to boost his claims for a spot in La Roja’s squad.