Aston Villa could lose one of their summer signings this month.
The 19th placed La Liga team are looking to shore up their defence and have targeted the Aston Villa defender as a player who is available this month.
Crespo, 28, only linked up with Midlands side over the summer, signing from Cordoba.
However, his experience in England has not been a good one.
He has just one Premier League appearance to his name - a 1-0 defeat to Stoke - and has not made the substitutes bench since the beginning of November.
He also played in the League Cup, falling to a 2-1 defeat to Southampton, and it is clear that Remi Garde does not rate the defender, who is able to play at centre-back and full-back.
The report claims that Rayo are looking to strengthen the left side of defence, and Crespo is the priority target having shown an aptitude for that position whilst playing in Spain.
He also has experience of the Spanish leagues, a trait the club consider vital, and is looking for a move back to La Liga, according to the report.
There are no indications that any offers have yet been submitted to Villa for his services.