The 23-year-old was regarded by many as one of La Liga's top players during his time at Valencia, and was part of Spain's 2010 World Cup-winning side.
However, many felt Mata had already achieved all he could at the Mestalla, and would benefit from a move abroad, which eventually materialised in August when Chelsea had a reported £23.5million bid accepted by Valencia.
Despite only having worn the colours of Chelsea for less than two months, Mata has already established himself as a key member of manager Andre Villas-Boas' squad.
And the Spain international admits he feels he has already taken the next step in his career, which was what he set out to achieve when he joined the Blues in the first place.
"This summer I took a major step in my career by signing for Chelsea and the truth is that everything is going well," Mata told AS.
"I feel comfortable playing [for Chelsea]."
Mata's arrival at Stamford Bridge has seen a marked improvement in the performances of compatriot Fernando Torres, who many feel will thrive feeding on his team-mate's deliveries.
And while Torres failed the find the net for Spain in Friday's 2-0 win over Czech Republic in Euro 2012 qualifying, Mata, who did score, believes it will only be matter of time before the former Liverpool hitman starts banging them in again.
"Torres did what the coach [Vicente Del Bosque] asked him to do and played well.
"Goals come in streaks and I'm sure he will have more luck soon.
"Torres is a great player and a great person."
Mata has already scored twice and laid on two assists in just six appearances for Chelsea.