Bristling John Kennedy insists 10-man Celtic were let down by inconsistency from ref Nick Walsh.
The Parkhead side were thumped 4-1 by Rangers after Callum McGregor was sent packing for two first-half yellow cards.
Kennedy took no issue with the midfielder's second - dished out seconds after Kemar Roofe's opening goal - but he reckons the initial booking was harsh.
McGregor fouled Ryan Kent and Kennedy claims Walsh told him the challenge was "reckless" at half-time.
But the Celtic interim boss disagreed before pointing to a later incident involving Odsonne Edouard as proof the whistler wasn't getting the big calls right.
Kennedy told Sky Sports: "It's a turning point but, again, OK, the second tackle he is on a yellow, goes to ground and gets a red card. That's fine.
"It's the first one, the yellow card. I asked the referee at half-time: 'What did you book McGregor for?'
"And he said: 'A reckless tackle'.
"Now I don't see any recklessness in it. He's on his feet, makes a genuine attempt for the ball and Kent's managed to nip in before him.
"There's nothing reckless in it.
"There's another incident on the far side where Edouard's breaking through into the final third and gets taken down by a slide tackle and we get a free-kick and that's it.
"There's no consistency there and that's what I'm most disappointed with. Red cards can happen but at least make the right calls."
