Manchester United could face a battle to retain a string of their most highly-rated young players in 2015.

The contracts of six stars - Tyler Blackett, Paddy McNair, Jesse Lingard, Reece James and Andreas Pereira - are due to expire at the end of the season.

All five players are, in theory, free to talk to foreign clubs from January 1 and sign a pre-contract agreement for next season, meaning that there is a danger that United could lose them for nothing come the end of the season.

Tyler Blackett's contract at Manchester United will expire at the end of the season

Blackett and McNair have both impressed following injuries to United’s senior defenders in the first half of the season. They were particularly impressive in the 2-1 victory at Arsenal.

United executives are understood to have held discussions over new a new deal for Blackett although a contract is yet to be finalised.

It is unlikely that these youngsters would choose to leave Old Trafford - such has been Van Gaal’s inclination to present them with opportunities - but it still seems curious that United have been sluggish in arranging extensions.

Young defenders Blackett and Paddy McNair (right) have impressed after being thrown in at the deep end

United fans will still remember, for example, how Paul Pogba was allowed to leave the club on a free to Juventus in 2012.

The one who may appear most likely to move on is 18-year-old Pereira, with sources in Belgium suggesting that he may be tempted to look for regular football elsewhere.

Adnan Januzaj, meanwhile, is likely to leave the club on loan in January.

Manchester United declined to comment.

Paul Pogba was allowed to leave Manchester United on a free contract to Italian club Juventus two years ago