Manchester United Reportedly to Make Formal Offer for Celtic's Kieran Tierney

Manchester United's pursuit of Celtic left-back Kieran Tierney is reportedly set to intensify, as they are expected to make a formal offer for him. 

According to David McDonnell of the Mirror, the 20-year-old is rated at £25 million, and United will step up their interest in him with a bid in the coming weeks, having scouted the youngster and been impressed with his performances.

His versatility appeals to manager Jose Mourinho, as he can also provide cover at centre-back or right-back, and he's viewed as better value for money than Tottenham Hotspur's Danny Rose, United's other top target, who is expected to cost twice as much.

Red Devils defender Luke Shaw looks to have little future at Old Trafford, having been repeatedly and publicly hauled over the coals by Mourinho. The coach's treatment of the 22-year-old has attracted criticism, per Sky Sports' Kaveh Solhekol:

Per McDonnell, Daley Blind and Matteo Darmian are also set to depart in the summer, leaving United with 32-year-old winger Ashley Young and little else in the way of options at left-back.

Young has performed well this season, but a new long-term candidate for the role is needed, and that's where Tierney could come in.

The youngster is still developing his game, but he's already an impressive talent.

He was named Scotland's Young Player of the Year last season:

Tierney has continued to go from strength to strength in this campaign. Scouted Football shared a look at his calendar year for 2017:

The Celtic starlet has played over 4,000 minutes in all competitions this season across 48 appearances—14 of which came in European competition—showing his importance to the side.

His ability to contribute in the final third has also been evident, as he has accrued four goals and nine assists in all competitions.

Celtic will be desperate to keep him having tied him down in October until 2023, but if he continues to develop at his current rate, he'll soon outgrow the Scottish outfit.

United represent a big step up from Celtic, and it's likely he'd need some time to adapt to his new surroundings, but he has the potential to shine at a high level.