ESSENDON coach Matthew Knights is supportive of the new rules to be trialled in next year's NAB Cup, but has warned the changes could alter the game if adopted for premiership matches.

Knight said the rules will take some adjusting to, highlighting the awarding of a free kick for a deliberate rushed behind, as well as the handing of a 50m penalty for holding up a player after he disposes of the ball.

"It's really refreshing to keep trialling new rules in the NAB Cup and if they're effective, the League and Commission can bring them into fruition," he said on Tuesday.

"The rushed behind is going to be very interesting in the NAB Cup with the free kick being where the rushed behind occurs.

"To watch that objectively it's going to be quite contentious."

But Knights was unsure if the penalty matched the crime under the new rule, with the free kick to be taken from directly in front of goal if the ball is rushed between the goal posts, and from the boundary line if it the behind is conceded through the goal and point posts.

"It is a big price to pay … it's basically another shot on goal. From a crowd and viewers' perspective it's going to make it really interesting."

Knights was also cautious on 50m penalties for holding out a player who had disposed of the football, saying the practice was so widespread that its policing would prove difficult.

"I think that's going to have a real effect on the game because there's a lot of blocking and retarding off the ball to prevent runners from breaking lines and moving into positions to receive," he said.

"It's going to be interesting now to see how teams combat those two new rules coming in."

Knights threw his support behind the interchange rules for the pre-season competition that will see no restriction on rotations, as well as the use of two 'substitute' players on top of the standard six on the bench.

"That gives us a good flexibility if you've got players coming back from long-term injuries that you might only want to play for a certain amount of time, like Adam McPhee or Jason Laycock," he said.

"I think that gives the coaches a good degree of flexibility to play a couple of those players that we just have to manage their loads."