Manchester United Transfer News: Kieran Tierney Update Amid Fresh Rumours

Manchester United will reportedly have a scout at the Old Firm derby between Celtic and Rangers on Sunday to cast an eye over Hoops star Kieran Tierney.

Per the Daily Mail's Jack Gaughan, the Red Devils have long been linked with the left-back. Manager Jose Mourinho's visit to Hampden Park for Scotland's friendly with Costa Rica in March is said to have been arranged so he could watch the 20-year-old.

Tierney missed the match through injury, but United are set to watch him again in Celtic's Scottish Cup semi-final clash with Rangers. Mourinho is eager to sign a new left-back in the summer because of Luke Shaw's continued struggles, Gaughan added.

It has long been expected that Shaw, 22, will leave United in the summer. He has faced persistent criticism from Mourinho and has started only one Premier League game this season, per BBC Sport's Simon Stone.

Ashley Young has been the Portuguese's go-to on the left side of defence this season, but the former Aston Villa man is not a long-term solution in the role, as he will turn 33 in the summer.

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Tierney could be, though. He has been an established part of the Celtic first team since 2015-16 and is a two-time Scottish Premiership champion and PFA Scotland Young Player of the Year award winner.

He boasts many of the attributes required of a modern full-back, as he is able to contribute both in attack and defence.

Tierney has already been capped nine times by Scotland, and although he is far from the finished article, he has enormous potential.

David McDonnell of the Mirror recently reported that Tierney is valued at £25 million.

That is a more than affordable fee for United and cheaper than a number of other targets would be, including Tottenham Hotspur's Danny Rose, as McDonnell noted.

It would be a gamble for United to sign Tierney because there is no guarantee he would be able to make the step up to the Premier League.

However, there could be few bigger matches for United to watch him in than an Old Firm derby, and if he impresses on Sunday, he would give his chances of a move to United a big boost.