Manchester United have agreed a provisional deal with Chelsea to sign Juan Mata for £40 million, according to the Guardian. However, the champions are yet to make a formal bid and any move still rests on Mata personally informing manager Jose Mourinho of his desire to leave Stamford Bridge. Negotiations between officials of the two Premier League heavyweights are at an advanced stage, and the transfer said to be "almost complete" by sources close to the discussions. Despite the lack of an offer from United for Mata, Chelsea expect that situation to change imminently with less than a week remaining of the January transfer window. Mata has found first team opportunities difficult to come by in west London this season and was left out of the Blue's league win over United on Sunday. The Spain star has made only 13 Premier League appearances this season - largely from the substitutes' bench - and has not played since New Year's Day. Still, there is reluctance at Chelsea to lose their Player of the Year for the past two seasons, a sentiment which has been expressed publicly by Mourinho himself in recent weeks. But with the World Cup looming, Mata will know he needs to be playing regularly to make Vicente del Bosque's final squad, and a move to United would boost his chances.