Lennon described the performance from his side as "unacceptable", but admitted that he did not expect his players to play that way.
"I'm confused, didn't envisage a performance as flat as that, particularly with freshening the team up," he said.
"It's my fault. I picked the team. I thought we had a strong team out on paper. There was no fluidity, we were too passive and there was no intensity to our play and we got what we deserved.
"The players coming have to do better. There was a malaise about the team today that I did not like at all. It is unacceptable. It's a dose of reality, back down earth with a bump."
Celtic still top the SPL table after earning 20 points from there first 10 games.