Amid strong reports Manchester United are interested in Mata, Chelsea would stand firm over their valuation for the Spain international.
As yet, there has been no formal bid from the champions but it is understood that Chelsea are bracing themselves for an offer.
The attacking midfielder - a £23.5m signing from Valencia in 2011 - has found first-team opportunities limited under Jose Mourinho this season, playing 90 minutes on just three occasions.
Reports of the 25-year-old's potential departure from Stamford Bridge have gathered greater momentum this week amidst reported interest from Manchester United.
David Moyes' side are seventh in the Premier league table and are in need of some fresh blood as they look to get their league campaign back on track.
Tuesday's newspapers claim the champions are set to make a move for the two-time Chelsea player of the year for a fee believed to be in the region of £37m.
One man who remains unconvinced by Mata's proposed arrival at Old Trafford is former Manchester United defender Gary Neville.
"That's a lot of money, 37 million quid, but they need a signing," Neville said on Monday Night Football.
"Does he fit with what I would call the typical philosophy of Manchester United? I would say no.
"The first question, I think, is where are you going to play? Wayne Rooney and Robin van Persie are up top if they are fit so where are you going to play him? Are you going to play him off the left or off the right?
"They would have to change to accommodate Juan Mata in the way they normally play. They normally play with wide players. Sometimes they tuck in, but generally they have wide players and the thing for me is where is he going to play?
"He's obviously a fantastic football player, there's no doubt about that, but one thing it does do, I suppose, is that David Moyes, Manchester United and Ed Woodward need to sign a big player."
Englander, Jose obviously doesn't see United as a direct rival for the league at the moment and, if you like daft conspiracy theories, it might make a b of sense. The theory goes that Chelsea have already played United home and away so he's willing to strengthen them so that they have more chance of taking points off Arsenal and City who really are direct rivals. Sounds daft to me, after all it's only 3 points, but some alleged experts seem to think it floats.- PolishJoe