26-year-old must be replaced: Three things we learned about Celtic in draw v Rosenborg
Ajer should be given first-team chance
Ajer, 19, made just his second appearance for Celtic since signing with the club from Norwegian outfit Start last summer, in what was his first start for the Bhoys.
Looking comfortable in possession, there was a sense of reliability about the youngster as he coped with Nicklas Bendtner easily.
With both Dedryck Boyata and Erik Sviatchenko renowned for their lapses in concentration, giving Ajer a run in the first team during the 2017-18 season.