The midfielder has cut a lonely figure on the Blues' bench for much of the campaign but, if the money is to be believed, a close on £40m switch to Old Trafford is now his most likely route out.
As of this morning the diminutive Spaniard was as short as 4/7 with online bookmaker Sky Bet to join Manchester United after starting the week as an 11/2 chance and turning the year at 25/1!
Sky Bet football trader Joe Petyt said: "We'd seen a few bets at big prices over the last month or so but on Sunday night the types of bets we were taking changed.
"We saw a few maximum bets at 11/2 and ever since customers have been taking whatever price we put up. He's now just 4/7 but that still hasn't put people off getting as much as they can on the move going through, " he added.
It would appear to finally signal a change of heart from the Chelsea hierarchy to the possibility of letting their popular player-of-the-year for the past two seasons move on.
This has led to Sky Bet opening a stay/go market and it's 8/15 that he will leave before the end of the current window and 11/8 that he stays.
One other possible option for Mata as he seeks to put himself in the frame for World Cup selection with Spain is a return to his homeland, possibly on loan. It's 20/1 that his destination is Atletico Madrid as they chase the La Liga title.