Chelsea are “playing hardball” over a fee for Juan Mata and want Manchester United to pay 42 million pounds to sign the playmaker, according to ESPN sources close to both clubs.

Mata wants to move to Old Trafford and the Blues are happy to sanction a deal, with the precise transfer fee providing the only major potential stumbling block.

There is still a strong belief that a deal for Mata, who missed training on Wednesday morning, will be completed by this weekend, but United must work out a breakdown of payments that is acceptable to Chelsea and negotiations are ongoing.

Jose Mourinho is believed to have provisionally approved the sale on Monday, as long as Chelsea officials are happy with all the details.

The Blues would still have preferred to sell to either Paris Saint-Germain or Atletico Madrid, but ESPN sources close to the negotiations have said Mata has made it known that his first choice is United. Atletico are, however, prepared to act in the unlikely event of the deal now collapsing.