Kieran Tierney is attracting plenty of interest (Picture: Getty)

Ex-Manchester United boss Sir Alex Ferguson approves of his former club’s interest in Celtic star Kieran Tierney, according to reports.

Jose Mourinho is keen on signing the Scotland international this summer and has had the defender watched on a number of occasions this season.

The Red Devils face competition from Arsenal, who are expected to enter the race for the 19-year-old with Kieran Gibbs expected to leave the Emirates.

However, according to the Manchester Evening News, the defender favours a move to Old Trafford and the Red Devils’ interest has been backed by Ferguson.

Ferguson backs a move for Tierney (Picture: Getty)

The Scot is said to be impressed with the Bhoys defender and approves of Mourinho making a move for the full-back.

Tierney’s arrival could throw Luke Shaw’s future at the club into further doubt, though the likes of Matteo Darmian and Daley Blind are expected to be the first to leave.

Ferguson, 75, is more involved at Old Trafford under Mourinho and regularly travels with the squad on away days.

Unlike under David Moyes and Louis van Gaal, Mourinho perceives Ferguson’s presence to be positive and the Scot was recently asked to attend training.

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