Valencia have announced they had reached "an agreement in principle" with Chelsea for the sale of Juan Mata to the west London club.
The Spanish club did not disclose the fee for the 23-year-old and also added the transfer was subject to the player passing the relevant medical tests.
New Chelsea boss Andre Villas-Boas has identified a lack of creativity in midfield as one area which requires improvement before the transfer window closes and will no doubt hope the Spain international can provide some nous to an ageing squad.
A statement on the Valencia website read: "Valencia Football Club has reached an agreement in principle with Chelsea FC for the transfer of the player Juan Manuel Mata. The agreement is subject to the relevant medical tests."
Chelsea are not the only English club reported to have shown an interest in Mata with north London rivals Arsenal and Spurs linked with a player who has flourished at the Mestalla after failing to make the breakthrough at Real Madrid.
Mata joined Valencia from Madrid in 2007 and has emerged as one of their most important players, his form earning him a regular place in the Spain squad.
He was a part of the party which won the 2010 World Cup in South Africa and was also a key man this summer as Spain won the Under-21 European Championship in Denmark.