Mata to 'undergo United medical'
An accord between the two clubs looks to have been reached shortly after Chelsea agreed a fee with Basel for Mohamed Salah who has been lined up as a direct replacement for the 25-year-old midfielder.
Mata will become United's club-record signing and a formal announcement is expected on Friday provided the playmaker comes through a medical today.
The Spain international did not train with Chelsea on Wednesday and is understood to have told team-mates that his departure from the club was imminent.
Chelsea are understood to be happy to sell and would make a significant profit on the man they signed for £23.5m from Valencia in 2011.
For Mata, the transfer would give him an opportunity for much more playing time with the World Cup in Brazil looming this summer.
All parties are keen for the transfer to go through, according to Sky Sports' Spanish football expert Guilleme Balague
"The idea is that Mata, who Chelsea are happy to let go, goes to Old Trafford in this transfer window," Balague revealed on Revista de La Liga.
"I am under the impression that a deal will be reached because it benefits everybody.
"United need quality, Mata needs to get out of the situation he is in and it would reinforce United for their meetings with (Chelsea's title rivals) Manchester City and Arsenal, which is clever from Jose Mourinho."