Cardiff City boss Neil Warnock was furious that Tom Lawrence did not receive a red card for his challenge on Sean Morrison.
The Bluebirds skipper entered into what appeared to be a 50-50 challenge with the Welshman, but after he cleared the ball Lawrence clattered into him.
It left Morrison crumpled on the floor as the game wore on into the dying minutes, but referee Darren England brandished only a yellow card.
It was Lawrence's fifth booking in the just seven this season, meaning he will miss the Rams' next match, but a furious Warnock believed the tackle was premeditated and dangerous.
"The referee had a good game but the only disappointment for me is that Lawrence should have got a red card," Warnock said.
"They’re nasty tackles, pre-meditated. Players should teach the referees about those things. Over the top that can break your leg, it’s craftily done. I thought the referee had a good game, I’m pleased with him.
"But when you watch it again, you’ll see it.
"You might not have noticed it because the referee didn’t. If you’ve played the game, I knew straight away he’s left his foot in. When you see it in slow motion, you’ll see what a horrible tackle it is."
The Bluebirds could earn only a draw against the Rams, meaning they are now winless in their four visits on the road this season but also unbeaten in their last four league outings.
