A disjointed Hoops side had no answer to the Highlanders’ spirited defensive display as a first-half penalty from Ross Stewart and a header from Alex Lacovitti from a corner late in the second half sealed a famous win for Stuart Kettlewell’s men.
The home side's defeat – Celtic’s first in a domestic cup competition for 35 matches – extends a poor recent run of form for the Parkhead side both at home and in Europe and leaves the position of manager Neil Lennon hanging by a thread.
Here's how the Celtic players rated in an abject performance.
Player ratings scale - 10: One of best performances you've seen. 9: Outstanding. 8: Very good. 7: Good. 6: Average. 5: Poor, 4: Very poor. 3: Terrible day at office. 2: Abysmal. 1: One of worst performances you've seen.
Here's how the Celtic players rated in an abject performance.