Mata played down rumours he was heading for Spurs originally.
He said: "That's not strictly true. The Chelsea offer was very important to me and the only one that was really worth considering.
"I just thought it would give me the opportunity to grow as part of a big club.
"Ever since I was a young boy I have been interested in the English league and Chelsea.
"I have always understood the importance of the teams that were fighting for Premier League titles. There were also a number of players I had my eye on. Like Jimmy Floyd Hasselbaink, for example."