THE AFL admits its umpires erred in not awarding Collingwood defender Nathan Murphy a free kick after he was clattered by Adelaide's Darcy Fogarty.

Murphy was positioned under a high ball in the last quarter of the Magpies' thrilling win on Sunday when Fogarty crashed into him, front on.

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The Magpie appeared to hold the mark but it wasn't paid, and he didn't receive a free kick either, despite the high front-on contact forcing him from the field with a bleeding nose.

Compounding the matter, play wasn't halted as Murphy was helped from the field, and the ball almost hit him and the Collingwood medical team as they headed to the bench.

Collingwood's Jordan De Goey soccered it over the boundary line, assuming play was to be stopped – but he was penalised for a deliberate out of bounds.

Magpies coach Craig McRae said he had "lost his mind" at the "staggering" umpiring blunder.

"Following a review today of that particular passage of play we acknowledge that the umpires missed the initial free kick and subsequently the process of managing the blood rule was not followed," AFL head of umpiring Dan Richardson said in a statement.

"We have been in contact with Collingwood to clarify the situation."

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Murphy told Collingwood's website he was left with "a bit of a fat lip" and "a bit of a broken nose" by the incident.

The normally calm McRae had lamented the entire incident.

"I lost my mind," McRae said.

"Because one, whether it was a mark or a free kick – either, you could argue.

"But then there's blood and he's trying to exit the field and we didn't get a chance to replace the player in the critical moment.

"I was astounded by it."

The AFL didn't provide an explanation why an obvious free kick to Ash Johnson in the dying minutes wasn't paid – though McRae hadn't planned to follow up on it.

The Collingwood forward, in the goalsquare, was clearly taken high by Adelaide's Jordon Butts.

"In the moment, I'm (thinking) 'What the hell is going on here?'" McRae said on Sunday.

"But then you move on. You can't do anything about it now, can you?

"You can go through every decision they made or didn't make, that is not where we live.

"We make way more mistakes than they do.

"You make mistakes and move on, that's the way I look at it."