Man United will send scouts to watch Kieran Tierney this weekend, according to reports.
Jose Mourinho has made signing a new left-back his No 1 priority this summer after Luke Shaw failed to convince him he can be a long-term option.
Celtic have an Old Firm derby this weekend against Rangers in the Scottish Cup semi-finals.
And the Daily Mail report United will have scouts at Hampden Park to have Tierney, 20, watched.
Mourinho travelled to Edinburgh for Scotland’s friendly with Costa Rica last month, where it is understood he had planned to watch the Celtic starlet, before he was forced to pull out through injury.
Scott McTominay also played in that game, but the trip was arranged before the United midfielder had officially pledged his allegiance to Scotland.
Mourinho has asked ex-Scotland manager Craig Brown, who he knows from his time studying north of the border for his Uefa pro licence, and enquired about Tierney’s development.
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The United boss has been forced to play Ashley Young at left-back for the majority of the campaign, as Shaw has failed to earn his trust.
Mourinho has been vocal in his criticism of the former Southampton man, and hauled him off at half-time in the recent FA Cup quarter-final clash with Brighton.
Shaw joined in the summer of 2014 on the back of a season in which he was named in the PFA Team of the Year, but his development has been hampered by a serious leg break.