Chelsea midfielder Juan Mata has reportedly been the subject of an informal enquiry from Manchester United.

According to ESPN, sources from both clubs have confirmed that United have contacted Chelsea regarding the Spaniard's availability, although it is unknown whether it was in relation to Chelsea's bid for Wayne Rooney.

Chelsea have maintained their stance that Mata is not for sale, and he is known to be one of owner Roman Abramovich's favourite players at the club.

However, after Chelsea reportedly opened talks with Anzhi Makhachkala midfielder Willian, the 25-year-old's place at Stamford Bridge could be in jeopardy.

The former Valencia player featured for 65 minutes against Aston Villa on Wednesday evening.