Chelsea beat rivals Manchester United on Sunday, and once more, Mata was consigned to the role of frustrated spectator as manager Jose Mourinho continued to show preference for other options in attack.
Newspaper reports linking the former Valencia man with a move away are now appearing on an almost daily basis, and Bleacher Report is here to keep you updated with all the latest storylines regarding Mata's future.
Will the Blues retain their former Player of the Year come February 1?
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Manchester United have announced the £37.1 million capture of Spain attacking midfielder Mata, who joins the club from Premier League rivals Chelsea.
The much-anticipated signing was officially announced on Saturday evening, with the club publishing a statement on their official website and running a series of programmes on their MUTV channel.
Per the statement, Mata said of his arrival:
I am thrilled to be joining United. I have enjoyed some very happy years at Chelsea but the time has come for a new challenge. United is the perfect place for me and I am excited at the chance I have to be part of the next phase in the club's history.
Chelsea is a top club and I have many friends there but you cannot turn down the chance to join Manchester United. I look forward to helping the manager and the team be successful in the coming years.
Mata will now be available to face Cardiff as part of David Moyes' side in the Premier League on Tuesday night. He also becomes the seventh World Cup winner in the club's history.
The move ends a recent spell on the sidelines at Chelsea for the twice Fans' Player of the Year and offers the chance of regular football ahead of the summer's World Cup in Brazil.
Following the announcement, Mata took to Twitter to thank Blues fans for their support over the past few seasons.
Friday 24 January
Chelsea manager Jose Mourinho has confirmed in his Friday press conference that Spain star Mata is set for a medical at Manchester United and explained his reasoning for the sale.
The Blues are, per reports that were backed up by the Portuguese manager to journalists, set to seal the capture of Egyptian Mohamed Salah in the coming days as a replacement.
Mourinho also played down suggestions that Mata should not be sold to a rival, praising the nature of Manchester United's conduct and bid.
Assuming there are no hiccups in Mata's medical proceedings, the move may well be announced officially later on Friday.
Thursday 23 January
If you are going to make one of the biggest deals in Premier League history, what better way to do it than to arrive at your new club in style?
Per the Mirror's Transfer Blog, that is exactly what Mata is doing this Thursday morning, as he travels by helicopter to his new base at Carrington.
There are still a couple of obstacles to overcome before the deal is likely announced later in the day, such as medical examinations, but all would appear to be in place for Mata to make a much-anticipated move.
Should the deal be confirmed ahead of the weekend, Mata would be available to face Cardiff with his new side on Tuesday evening.
Wednesday 22 January
Manchester United have agreed terms with Chelsea for the £37 million transfer of Mata, according to the Telegraph's Jason Burt and Mark Ogden.
The reports came as little shock after a day of increasing speculation on Wednesday, but represents a rare major internal Premier League transfer between competing sides near the top of the table.
The report states:
Chelsea have accepted a £37million bid for Juan Mata and immediately released the Spanish international to join Manchester United to complete the most dramatic deal of the transfer window.
Mata will undergo a medical on Thursday at United before completing the move that will see him more than double his £70,000-a-week Chelsea salary at Old Trafford.
All eyes will be on United's Carrington training ground and Manchester hospitals on Thursday, as the switch seemingly nears inevitable completion.
Coming within minutes of United's Capital One Cup exit, the latest reports will be a boost to the Red Devils' supporters after what has been a difficult few weeks.
Tuesday 21 January
A potential move to Manchester United took a step closer on Monday, with the Independent's Sam Wallace and Ian Herbert reporting that Chelsea will accept any offer of more than £40 million.
The report states:
Tuesday 21 January
Manchester United are set to make a bid of £37 million for Chelsea playmaker Juan Mata, according to the Guardian's Dominic Fifield and Jamie Jackson.
The article, which cites concerns over his World Cup place as the reason for Mata's desire to leave, states:
Chelsea are braced to receive a club record bid from Manchester Unitedfor their unsettled attacker Juan Mata, an offer which will test the London club's resolve to retain the Spain international despite his fringe status in the first team this season.
A number of news outlets reported the same story on Tuesday morning and, while United have confirmed that they have not yet made any bid for the player, there would appear to be some truth in the reporting.
David Moyes side currently lie six points off fourth place and qualification for next season's Champions League, with 16 games of the season remaining.
After what was a botched effort in the summer transfer market, the club are determined to make amends this month and Mata may well be just the tonic needed for the club and its fans at the current time.
Will Chelsea and manager Jose Mourinho be willing to sell to a side considered to be a pre-season rival of the Blues? That may be the deciding factor.
Monday 20 January
The only real update on Mata's situation over the weekend came courtesy of Dean Jones of the Sunday People, who reports that Manchester United are continuing to hold interest in the No. 10.
While the article's headline of "Chelsea's Juan Mata nears Stamford Bridge exit" may suggest a move is close, Jones himself admits that a move this January is unlikely—despite Chelsea's hope of including Wayne Rooney in any negotiation.
Manchester United have made contact in hope of doing a £20million deal but a loan move to Atletico Madrid seems the most likely option now for the Spanish midfielder.
Mata’s father, Juan senior, acts as his agent and made a trip to London to discover whether he will be given more game time between now and the end of the season. But Chelsea officials could not make any promises and Mata is ready to seek a move.
The Blues, who value Mata at £30m, were previously interested in a United deal if it involved a swap with Wayne Rooney but that now seems unlikely.
For Chelsea's part, manager Mourinho began the weekend by expressing his belief that Mata still has a "big role" to play for the Blues this season.
Speaking to BBC Sport's Football Focus programme, the Blues boss discussed his hope of retaining the Spaniard, but conceded that it must be hard for the player to sit on the bench after previously being considered a key player.
Whether he will remain a Blue remains far from clear.
Monday 20 January
Former Blues midfielder Michael Ballack is the latest big name in the world of football to call for greater inclusion of Mata in the Chelsea side.
Ballack was an important player in the late stages of Mourinho's first stint as Chelsea manager, but admits he cannot comprehend why the previously first-choice Spaniard is no longer being given regular playing time.
Per Tony Stenson of the Daily Star, Ballack said: “I can’t understand why Mourinho is having trouble to get his best from his forwards and I think not playing Mata is a mistake.”
Unfortunately for Mata, Chelsea's 3-1 win over Manchester United on Sunday only adds further justification for his omission.
While Eden Hazard was the biggest threat from attacking midfield, the defensive commitment of both Oscar and Willian was a big factor in keeping the Red Devils quiet, too.
The saga is set to rumble on. With only 11 days of the window remaining, at least we can be thankful that there will soon be a definite answer—until the summer, at least.