Manchester United chiefs are frustrated over the emergence of Michael Keane at Burnley.

The Sun says they are “kicking themselves" for NOT putting a sell-on clause in £25m-rated new England defender Keane's contract when he moved to Burnley.

The 23-year-old centre-back is having a break-out season in the Premier League and has been linked with a mega-bucks move to Chelsea in January.

A United insider revealed: “The club is kicking themselves over it and some people are now keeping their heads down.

“There is a fear they could be hearing 'we told you so' in the near future. He has always been highly-rated by United's reserve coaches."