Hamilton gaffer Brian Rice is adamant that Leigh Griffiths should have seen red for his stamp on Sam Woods.
The flashpoint came just 13 minutes into the clash and with Celtic facing the remainder of the match with 10 men, the Hoops would have surely been facing a difficult task.
And Rice reckons the result hinged on that single moment and the referee's decision not to send the striker off.
He said: "I don't think there is any debate it was a red card for Leigh Griffiths.
"There is no debate. But my opinion doesn't matter and the only person whose opinion matters is the referee and he called it the way he has seen it so we move on.
"He may look at it and say he made a mistake or he may look at it and say he got that right but in my humble opinion I don't think there is any debate.
"A big decision by the referee changed the game. My boys fought heroically.
"At 1-0 everything we worked on was good, I felt OK and I felt it was very harsh how it ended up.
"Celtic ended up with seven attacking players of real quality. But the biggest turning point is definitely the refereeing decision. One decision led into another but it is only my opinion."
Neil Lennon admitted that he talked to Griffiths about discipline but denied there had been a stamp.
Lennon said: “I didn’t think he stamped on him. But he pushed the guy in the chest and that’s not what I want.
“Ill discipline isn’t what we’re about - we try to keep our discipline. I had a word with him and he calmed himself down.”
