Tierney is likely to start for Celtic in their Scottish Cup semi-final tie against Graeme Murty’s Rangers at Hampden Park on Sunday afternoon.
It has been reported by The Daily Mail that the European giants, who have won the Champions League three times and are one of the biggest clubs in the world, will have a scout at the game to observe the 20-year-old defender.
It has also been reported that United manager Jose Mourinho wanted to watch the left-back in action in person at Hampden Park last month during Scotland’s international friendly against Costa Rica, but the youngster had to withdraw due to injury.
Tierney, who can operate as a centre-back or as a left-back, is one of the best young defenders in Europe.
The Scotland international will be a key player for Celtic against Rangers, and it should not be come as a surprise if he impresses the United scout in attendance.