Celtic taught a lesson by superior opposition in Europe. Nothing much is new there, but what remains to be seen is if they take their newfound knowledge on board.

Leverkusen cruised to their 4-0 victory and had it in the bag after 25 minutes, with Celtic showing little sign of life after the opener, aside from a pacey start to the second half that yielded no results.

How much of an issue is it, when Celtic fall behind they seem devoid of energy and ideas to salvage the situation?

READ MORE: Celtic's electricity falters when tested and going behind feels irreversible

The run of form needs abruptly stopped at Pittodrie on Sunday, against an Aberdeen side in an equal state of flux. The goodwill Ange garnered in his first month or so can't last forever, but time and context are needed. If Aberdeen stop Celtic from winning, how much more sand will slip through the hourglass' channel?