The centre-back has enjoyed a brilliant year with Celtic and is now a target for the German giants who are desperate to bolster their backline.
Dortmund have reportedly already made contact with the Scottish Champions, but Celtic are keen to keep the Norwegian international given his outstanding potential.
The 19-year-old’s career began with IK Start in Norway where he captained the side at 16. The teenager moved to Scottish champions Celtic in 2016 and spent the season on loan at Kilmarnock before returning to the first-team this campaign.
He’s since made 24 appearances in all competitions under Brendan Rodgers but could be on the move if Celtic are faced with a big bid from a suitor.
The Scottish giants aren’t in a rush to sell, however, as Ajer is contracted until 2020. He has all the traits of a modern day centre-back and may be too valuable to lose just yet.
The talented defender could prove to be a great signing for Dortmund in the future. It’s unknown if he’s keen on a move to the Westfalenstadion, but Celtic wanting to keep him might prove to be the biggest obstacle.