LINDSAY Thomas should have been paid a free kick for a high tackle by Grant Birchall in Friday night's match against Hawthorn, umpires coach Hayden Kennedy has said.

The incident helped spark North Melbourne coach Brad Scott's post-match accusation that umpires had said to his players they did not pay free kicks to Thomas because they believed he ducked.

Kennedy, speaking on Whistleblowers, said it was clear Birchall's arm was over Thomas' shoulder.

"You can see that Lindsay does get taken high by Grant very quickly," Kennedy said.

"It's only brief, but [with] the slower motion from a different camera angle, you can see that the arm does go high.

"Lindsay deserves a free kick on that occasion."

Kennedy said the umpires were surprised at Scott's claims, which were later proven to be inaccurate and a case of miscommunication, with North Melbourne withdrawing the comments a day later.

"I was at the game and we've got match (communications) into our box, so we can hear everything that's been said by the umpires.

"So I was pretty sure on the night that we hadn't stepped over the line in regards to that, and I was confident that we did everything how we're instructed to do it."

Umpires were angry about the comments, but accepted North Melbourne's apology, Kennedy said.

AFL CEO Gillon McLachlan has said the situation will be addressed in the next 24 to 36 hours.

"The most important thing was that it was dealt with quickly by both the AFL and North Melbourne, which was great," he said.

"The umpires were quite unhappy with the way things progressed.

"They felt their integrity was questioned, so it was great to get it cleared up really quickly."

The AFL started its trial of four field umpires in the bye rounds, and Kennedy declared it to be a success, especially in Friday night's match between the Kangaroos and the Hawks.

"There were about six or seven free kicks paid by the non-controlling umpire which were really well-deserved on the night.

"I just got off the phone to one umpire who's said he's pulled up completely differently to what he would under the three-umpire system."

Kennedy said they would look at the results of all three weeks' trial before deciding on the umpire set-up for next season.

"It's certainly a work in progress, but the feedback is it's pretty positive at this stage."