"I think it's normal in every transfer window that there are lots of rumors but I'm happy here," Mata said.
At the international level, Mata was a surprise omission from the Spanish national team squad for upcoming World Cup qualifiers.
Chelsea was busy in the transfer market over the offseason and the signings of Marco van Ginkel, Andre Schuerrle, Willian, Christian Atsu, as well as Kevin De Bruyne returning to the club after a spell on loan, have intensified competition in Chelsea's attacking positions.
After leaving Mata out against Manchester United last month, Mourinho denied that the Spaniard's future could be in doubt.
"Everything is clear between me and the player. We have no problems," Mourinho said. "I think he's a very important player for us. He wants to be a very important player for us. He wants to stay. I want him to stay, the club want him to stay. There is no story."