Jose Mourinho will have the final say, and it would require a thaw in relations between the clubs before the sale of 25-year-old Mata to Old Trafford.
A loan move to Atletico Madrid is another possible route for Mata.
Mata was player of the year at the club for the previous two seasons and has started 11 Premier League games this season, equal, for instance to the number of league games started by Fernando Torres and Cesar Azpilicueta.
The bid by United underline their increasing desperation to make a signing this window, The Independent reports. (ANI )