The Hoops boss started with a back three of Efe Ambrose, Thomas Rogne and Kelvin Wilson but changed it to a back four after Leigh Griffiths rounded Parkhead goalkeeper Fraser Forster to score the winner from an acute angle.
Afterwards the Celtic boss, whose side had won their previous six games, said: "Frustration is the key word.
"First of all I would like to say it was a great atmosphere and a great game, played in a great spirit. But I am not disappointed in our performance at all.
"I am disappointed with the goal, obviously, and I am disappointed with my own formation, which I changed, so I will take the blame for that. We had two formations set up and I chose the wrong one by the look of it.
"The three didn't really work for us and once we went to a flat-back four we were more in control and for 70 odd minutes we dominated the game.
"I was disappointed with the final ball and composure in front of goal but, on another day, we would have won the game comfortably.
"So in terms of attitude, desire and intensity I can't fault the players at all. It was there for all to see, we just lacked the edge in front of goal and the lack of bodies in the box was apparent.
"There is no excuse. I am not making excuses, I am pretty pleased with the way we played.
"I don't like losing, as you know, but there is a way of losing I suppose when you are having a go for 70-odd minutes, that's the way to lose."