RULE changes to combat congestion are not inevitable next season and might not be introduced until 2021, AFL football operations manager Steve Hocking says.

Speculation was rife multiple changes would be made to the game from 2019 after Hocking said on Tuesday he would be tabling three or four proposed rule tweaks at next week's Competition Committee meeting.

Hocking also said any rules amendment would involve several tweaks given clubs could adapt to a single change in the following pre-season.

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However, the League footy boss stressed on Thursday that change next season was not a forgone conclusion.

"Let's understand that we're not talking potentially of this happening in 2019. It has to go through the competition committee, it's got to go through the AFL executive, it's got to get to the Commission," Hocking told SEN radio.

"Having spent 10 months with the Commission, they're super impressive people. There's no way known on (chairman) Richard Goyder's watch that he's just going to pull a lever and go, 'Right, let all this roll through.'

"There's going to have to be so much work and evidence and also understanding, and everyone's got to be ready for it.

"It may not be next year, it could be the year after, it could be the year after that."

The League's recent trials with Hawthorn, Brisbane and Fremantle involved such things as structured starting positions at centre bounces and stoppages, an expanded kick-in area of 25m, and the last-touch out-of-bounds rule, while reduced interchange rotations is another change being seriously considered.

These trials were conducted over 10-minute halves. A similar trial will be conducted by St Kilda in two weeks' time, while Hocking has plans to run full-game trials at the end of the home and away season, potentially with the state league teams of clubs involved in the AFL finals.

Asked on Thursday whether a limited series of trials was enough evidence to base rule changes on, Hocking said: "Absolutely not."

But he pointed out that "hundreds and hundreds of hours" work had led up to those trials, and more work was yet to be done.

"At no stage are we going to make a decision whereby it's contrived or whereby Nathan Buckley feels like it's a blight on the game," Hocking said.

'''Bucks' has got the game absolutely at heart. He is one of the coaches who comes up out of it and understands because he's actually been part of the Laws (of the Game Committee) previously and we welcome that."

Hocking said he understood some fans were "nervous" about how any rule changes would affect the game, but was adamant their concerns were unfounded.

"We've got a group of people (at the AFL) who are from club land that understand the game and are caring for the game, and then wrapped around that we've got a competition committee that cares for the game and (consists of) varying voices," he said.