The Spain international swapped life at the Mestalla for that at Stamford Bridge over the summer.
He has settled quickly in England but will be back in his homeland on Wednesday night in the UEFA Champions League.
It promises to be an emotional night for Mata as he prepares to line-up against former domestic colleagues.
Some players find it difficult to go back to their former clubs, especially ones where they are still held in high regard.
Mata, though, believes he is professional enough to handle the occasion and play his part in what he hopes will be a productive evening for his new employers.
"It is going to be strange for me," he said.
"I was here for a few years and it's going to be odd for me to go into a different dressing room.
"It will make it special for me. I know about the atmosphere in the Mestalla when Valencia play in the Champions League. I know how special the game is going to be and I'm very happy to be here.
"But I don't know if it will be hard for me to play against my former team. We will find out what it feels like.
"I'm focused on helping the team win. Before and afterwards I will say hello to my friends here but the focus is on helping Chelsea win."
Blues boss Andre Villas-Boas has no concerns regarding Mata's state of mind and is believes he will be a useful attacking weapon in midweek.
"Different players react differently coming back home, so the question is correct," he said.
"David Villa reacted differently when he came back here for the first time with Barcelona.
"But we bought Juan because we believe in his style of play and creativity."