North Melbourne coach Brad Scott says it would be nice if next year's pre-season cup involved a trial of the new three-interchange rule.

Next year in the home-and-away season, all clubs will field three interchange players and one substitute, with the sub able to be used at any time and the player he replaces not eligible to return to the field.

"It would have been difficult to trial the substitute rule but it would have been something that would have been nice to have seen in action at the NAB Cup with the reduced numbers," Scott told reporters at Arden Street on Wednesday.

"But by the same token we also want to play eight players on the bench in the NAB Cup (pre-season competition).

"All the rule changes are valid and we'll see how they work. That's what the NAB Cup's designed for, to trial new rules."

Scott backed the AFL's video replay rule trial for the pre-season cup, saying it's a "no-brainer".

After a series of goal-umpiring blunders, the AFL will allow the official scorer to assist goal umpires with scoring decisions if a video replay is immediately available in the pre-season cup in February.

"It makes perfect sense. The logistics are the only issue," Scott said.

"If we can keep the game flowing and not have to wait too long to get decisions, it really is a no-brainer that you use the technology if it's there.

"The only issue we would have is if it slows the game down too much, which I don't think it would."

Another rule to be trialled in the opening round of the pre-season cup is the awarding of a free-kick against the last player to touch the ball before it goes out of bounds.

The Kangas, who finished ninth in 2010, face a tough opening to the pre-season cup with matches against Geelong and Western Bulldogs at Skilled Stadium on February 20.

Scott said he was confident Leigh Adams would be fit to resume training in January despite a heart operation on Thursday which the coach described as a "standard procedure".

"We all think we're going well. That's because there's no opposition out there," Scott said.

"We're quietly confident with the way we're going. We think our good players are training really well and we've got some young guys who might surprise a few people."

Scott said skipper and five-time club champion Brent Harvey, 32, continued to amaze him.

"While he keeps performing like he is at the moment during pre-season, there's no telling when he'll finish up," Scott said of the Kangaroos skipper.

Scott said the club had good reason for optimism.

"Luke Delaney and Robbie Tarrant are someone we hope who can come in and play key-position roles for us," he said.

"I still see Lachie Hansen as a key-position player, whether it's in the front half or the back half.

"We're pretty excited about the young guys coming through and it's not just the midfield."

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