The Norway defender and French midfielder were not included in the Hoops squad registered with UEFA ahead of the first leg of the Champions League qualifier against Danish side Midtjylland at Parkhead on Tuesday night.
Ajer has had a fitness issue but he has been heavily linked with a move to Brentford while there has been speculation about the future of Ntcham, who was sent out on loan to Marseille in the second part of last season.
When asked about the Norwegian, Celtic boss Ange Postecoglou said: "I'm concentrating on the ones who are involved. I can't afford to waste time on anyone other than the ones who are here and committed to being here."
Recent recruit Osake Urhoghide is in Postecoglou's squad but fellow new signings Liel Abada and Kyogo Furuhashi have not been included.
There is scope for Celtic to add two players to the squad before midnight tonight.