The German side ran out 4-0 winners at Parkhead, a result which leaves Ange Postecoglou's men bottom of their group after two defeats in two.
Celtic created plenty of good openings but came up against an inspired Lukáš Hrádecký in the Leverkusen goal making a number of excellent saves. At the other end of the pitch, however, it was a different story as the home side gifted the German side two first-half goals.
Bayer added two more after half-time despite a spirited performance at times.
So, how did the players involved rate out of ten.
Player ratings scale - 10: One of the best performances you've seen. 9: Outstanding. 8: Very good. 7: Good. 6: Average. 5: Poor, 4: Very poor. 3: A terrible day at the office. 2: Abysmal. 1: One of the worst performances you've seen.

13. Nir Bitton - 5
Not much of a positive influence off the bench but a difficult game to come into. Photo: Ross MacDonald - SNS Group

14. Albian Ajeti - N/A
Fifteen minutes or so and no impact. Photo: Ross MacDonald - SNS Group

15. Giorgos Giakoumakis - N/A
First sighting off the Greek striker on late. Hard game to come on and make an impact. Photo: Ross MacDonald - SNS Group

