The Chelsea man has been the subject of much speculation throughout the summer and since the start of the season, after losing his first team place under new manager Jose Mourinho.
Reports suggest several clubs are interested in signing the 25-year-old in January, with former club Valencia adding their name to a list that already includes Arsenal, Tottenham, Manchester United and Real Madrid.
Despite strong interest from the north London duo in particular, it is Valencia who believe they are in pole position to bring the Spaniard back to the Mestalla Stadium.
Reports in Spain suggest the club have already begun the process of speaking to sponsors and local businesses in the hope of raising the £25million they believe would be enough to secure his services.
Mata only completed his switch from Valencia to Chelsea in 2011, and since then has shone at Stamford Bridge.
The Spaniard has picked up a Champions League, FA Cup and Europa League winners medal with the Blues, whilst being voted their player of the season two years running.
However with Mourinho unable to give him first team assurances, Mata may well seek a move away in January, knowing he will need to be playing regular first team football ahead of next summers World Cup.