The Norwegian centre-back’s performance led to comparisons with Liverpool star defender Virgil van Dijk. (h/tThe Daily Star UK)
After suffering a knock in last week’s Premiership game against Dundee, Ajer remained a doubt to start against Spaniards.
Later, the manager, Lars Lagerback denied the injury concerns and said Ajer would be his key man in the clash against the 2010 world cup winners.
Despite the 2-1 defeat, the Hoops centre-back was lauded by the fans on twitter comparing with the Dutch defender.
Ajer joined the Park Head side back in 2016 and has been a consistent figure till now.
The 20-year-old has made 20 appearances this season and his notable performance came against Valencia in the Europa League clash despite losing the game.
With the defenders Dedryck Boyata and Filip Benkovic speculated to leave Park Head this summer, Ajer is the only option left for Neil Lennon.
Lennon was appointed as the Hoops manager on an interim basis after Brendan Rodgers left the side to join Leicester City.
The former Celtic captain has led his side to pick up ten points since taking the charge.
The former Celtic captain’s future also remains uncertain as the club is reportedly in search of a new full-time manager.
The Hoops are currently leading the Premiership table ten points clear of their arch-rivals Rangers.
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They are set to play the Old Firm derby this Sunday at Celtic Park.