The Spaniard was set to arrive by helicopter on Thursday, but Chelsea's desire to secure a move for Mohamed Salah has forced the Red Devils to shelve their plans temporarily
Manchester United are not concerned by the delay in signing Juan Mata from Chelsea and still expect to wrap up the deal.
Mata was due to fly into Carrington by helicopter on Thursday, with the club erecting a temporary helipad within the training centre.
|MATA TO MAN UNITED
HOW GOAL COVERED THE STORY
|CHELSEA OPEN TO MATA EXIT
|MATA ON VERGE OF UNITED SWITCH
|CHELSEA TARGET SALAH
|MATA FLIES IN TO COMPLETE DEAL
|WENGER: MATA MOVE IS UNFAIR
United believe Chelsea's negotiations for Egypt international Mohamed Salah, effectively Mata's direct replacement, put a brake on proceedings, while poor flying conditions increasingly became a factor as the day wore on.
The Premier League champions, therefore, are confident that the £37 million club record signing will be finalised, but must wait for Salah to complete his move to Stamford Bridge.
Mata was expected to make his United debut against Cardiff City at Old Trafford next Tuesday, but with the deal dragging on he may have to wait until the trip to Stoke City on February 1.
The match against Ole Gunnar Solskjaer's Cardiff will come exactly a week after talks over Mata accelerated. Informal discussions between the two clubs were held at the beginning of this week, with United weighing up a formal bid and Chelsea prepared to sell.
The deal had moved at remarkable speed since then, with Jose Mourinho sanctioning Mata's sale to facilitate the purchase of Salah from Basel. The Spaniard edged closer to United on Wednesday after missing first-team training, and it emerged later that evening that Salah was lined up by the Blues.
However, with Chelsea having so far failed to push through a deal for the Egyptian, proceedings have slowed.
Arsene Wenger complained on Thursday that the timing of the Mata transfer is unfair, given that the 25-year-old playmaker will not have to play against his former club for the Red Devils this season, but will feature against Mourinho's title rivals in Manchester City, Arsenal and Liverpool.