Manchester United boss Jose Mourinho is reportedly fearful that he could lose number one goalkeeper David de Gea on a free transfer to Juventus.

De Gea's current deal with United will expire at the end of this season, and despite the Red Devils having the option of a 12-month extension, there remains huge uncertainty surrounding the Spaniard's future.

De Gea has long been linked with a move to Real Madrid, but the European champions signed Thibaut Courtois from Chelsea during the summer, and no longer appear to be in the running.

The 27-year-old is believed to be weighing up his future at Old Trafford, however, with United currently struggling to challenge for the major trophies.

According to The Sun, Mourinho fears that Juventus, who recorded a 1-0 win against United in the Champions League on Tuesday night, could land De Gea on a free transfer.

The report adds that De Gea is aware of the interest from the Italian champions, who lost Gianluigi Buffon at the end of last season.

De Gea has made 327 appearances in all competitions for United since a 2011 move from Atletico Madrid, and has won one Premier League title, the FA Cup and the League Cup during his time at Old Trafford.