Speculation continues to rage over the future of the five-time Ballon d'Or winner, who is understood to be unhappy in the Spanish capital due to Madrid's struggles on the field this season as well as matters off the pitch.
Ronaldo was accused of tax evasion by Spanish authorities last year and reportedly asked to leave the club in the summer, with Manchester United heavily linked with a move to bring the Portuguese back to Old Trafford at that stage.
Ronaldo spent six years at United before joining Madrid, and would reunite with former Madrid boss and fellow countryman Jose Mourinho if he returned to the club.
However, Spanish publication Don Balon reports that Chelsea have surprisingly emerged as the 32-year-old's preferred destination.
Ronaldo is understood to be keen on the idea of a switch back to the Premier League, while Chelsea would also be interested in bringing the reigning world player of the year to Stamford Bridge due to the uncertain nature of Eden Hazard's future at the club.
The report also claims that United have cooled their interest in their former player, who has scored only four La Liga goals so far this season.