By Editor Wayne Veysey | 17 years experience of breaking major stories at Evening Standard, PA and Goal, including exclusives like this

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Liverpool scouted Celtic left-back Kieran Tierney in their Scottish Cup defeat to Rangers on Sunday, Football Insider sources understand.

The Merseysiders assessed the highly-rated teenager in the Old Firm clash at Hampden Park as Celtic crashed out of the competition on penalties.

Tierney played the entire 120 minutes of the match, which finished 2-2 after extra time before Rangers won 5-4 in the shoot-out.

A Liverpool recruitment source has told Football Insider that teenager Tierney is on a shortlist of potential new left-backs that includes Leicester’s Ben Chilwell, Lorient’s Raphael Guerreiro, PSV Eindhoven’s Jetro Willems and Cologne’s Jonas Hector.

Liverpool are willing to pay between £5million and £10million this summer for someone to compete with first-choice Alberto Moreno on the left side of the defence.

Celtic legend Pat Bonner claimed Tierney and substitute Tom Rogic were the only two Celtic players to emerge from the crushing defeat to their arch rivals with any credit.

“Young Kieran Tierney was one of the best players but they rest of them didn’t really perform, until Rogic came on,” former goalkeeper Bonner told BBC Sportsround, as quoted by the BBC website.

“It is hugely disappointing for Celtic. They should have enough in that team to go and perform better than that in the first half and take the game to Rangers.”

Tierney, 18, has enjoyed a whirlwind campaign in which he has made 29 appearances for the Scottish Premiership leaders and been handed a Scotland call-up.

Red alert: Moreno faces growing competition for his place next season

Red alert: Moreno faces growing competition for his place next season

He made his full Scotland debut against Denmark during the recent international break despite never having pulled on a dark blue jersey for the Under-21s.

The teenager has already been linked with a lucrative move to Southampton and now Liverpool are keeping close tabs on him.

Celtic manager Ronny Deila is adamant the youngster is going nowhere this summer and has called on him to stay at the club for up to three years but is convinced that Tierney can one day roll back the years by treading the same path as Scotland all-time greats to one of the biggest clubs in Europe.

In other Liverpool transfer news, Klopp has already begun to look towards a summer revamp with his scouts checking out a potential £12million player.