The Spaniard has been linked with a move away from London this summer, with some reports claiming that manager Jose Mourinho didn't include the 25-year-old in his plans for the club.
However, Mata maintains that he was not bothered by the speculation and that he is focussed on matters on the field.
"I was relaxed about the speculation because I spoke to the club and the manager, who said I was important to them. That was good to hear," Mata is quoted as saying in several newspapers.
He added on Chelsea's official website: "We're really looking forward to starting the season with him and we are all excited about it. Jose did a really great job here a few years ago and I think that we can do it again.
"It's very good, everyone wants to feel important for the club, I feel it, I'm very happy and enjoying training with the new manager, and I hope I can improve on the last two seasons."
Mata is entering his third season with Chelsea having joined from Valencia in 2011.