Manchester United are tracking Celtic teenager Kieran Tierney, whose reputation continues to enhance north of the border.

Head of scouting Marcel Bout took in the Old Firm draw against Rangers earlier this month and a United representative is likely to attend Sunday's Scottish Premiership game at Hearts.

The 19-year-old left back is already in his second full season and impressed in the 3-3 Champions League draw with Manchester City back in September.

Scotland defender Kieran Tierney (right) has been watched by Manchester United this season

Tierney impressed during Celtic's Champions League draw with Manchester City last year

KIERAN TIERNEY FACTFILE Age: 19 Position: Left back Clubs: Celtic (2005-present) Appearances: 66 Goals: 2 Advertisement

Scouts had been keeping a watching brief before then, but Tierney's buccaneering display drew further attention.

The switch to right back last weekend, during Scotland's slender victory over Slovenia, will also do his case no harm as Arsenal circle. It is thought Celtic would demand upwards of £10million.

Tierney claimed afterwards Gordon Strachan's surprise selection at Hampden Park was something he relished, which will have interested United further.

Jose Mourinho is on the hunt for full backs this summer, with a question mark over the futures of Luke Shaw and Matteo Darmian.

Defender Luke Shaw (left) has fallen out of favour under manager Jose Mourinho this season

Manchester United are also considering a move for Celtic's in-form striker Moussa Dembele

Darmian would prefer a switch back to Italy if he was to leave Old Trafford after filling in a number of roles this term.

The 27-year-old's potential departure would see United requiring a defender just as versatile, with constant checks being made on Tierney.

United are also known to have looked at Celtic's top scorer Moussa Dembele.