Transfer news: Wayne Rooney row with Chelsea is factor in Manchester United using third party deal to sign £37m Juan Mata

Manchester United’s highly unusual use of intermediaries to conclude the Juan Mata deal may have stemmed from their strained relations with Chelsea after last summer’s dispute over Wayne Rooney.

United are likely to have been turned down flat, had they called Chelsea asking for permission to speak to Mata, after being made aware of his desire to leave west London. Though the details of how the deal has been done are yet to emerge, the possible sequence of events is that Mata instructed his agent to find him a new club, United were made aware through a third party, but then needed an intermediary of their own to begin discussions.

The club could not have approached Mata directly or they could have faced the same charges of trying to tap up a player which resulted in manager David Moyes’ former club Everton being hit with a £45,000 fine and embarrassed this week. The identity of United as the club with principal interest in Mata could therefore have been masked by intermediaries until it became clear that there was business to be done. Then they made their move.

The deal – which is likely to see the 25-year-old undergo a medical at Carrington today – reveals the way that intermediaries and agents can get in on the action when clubs are unable to do business with each other. The alternative explanation of United’s use of a third party is that they wanted to call in transfer market experience which they possessed when Sir Alex Ferguson and former chief executive David Gill ran the club.

United are understood to have had no contact whatsoever with the influential businessman Kia Joorabchian, who took Carlos Tevez from United to City in 2009 and who has been on the edges of this deal.

United’s nightmare season showed no sign of easing when they learned that the twisted ankle sustained by midfielder Michael Carrick against Sunderland on Wednesday night will keep him out for at least three weeks. Carrick was in great discomfort when he arrived at Carrington yesterday and though United are hopeful that he has avoided the lengthy lay-off that comes with torn ligaments, there is an anxious wait for scan results to reveal the full picture.

The Carrick situation is a particular concern for United, with Anderson now out on loan at Fiorentina, Marouane Fellaini still recovering from a wrist operation and Darren Fletcher only recently back from serious illness. That leaves only Tom Cleverley, 40-year-old Ryan Giggs and Phil Jones, who is best suited to centre-half. Even three weeks out would mean Carrick, who missed 10 successive games with injury in the autumn, will be missing from the fixtures with Cardiff City, Stoke City, Fulham and Arsenal and only return for the final 12 weeks of the season.

United are likely to announce Mata as their player today but the club share price dropped from $15 (£9) to $14.85 yesterday, only just above the 12-month low of $14.75. Even Fifa are now having their say on the club’s problems. A feature in the world governing body’s latest weekly magazine is entitled: “United at the crossroads.” It argues that “radical change could be the only solution”.