The reduced interchange cap could cost a side a win if not tweaked to factor in players leaving the field under the blood rule, North Melbourne coach Brad Scott says.

Scott questioned the rule after Drew Petrie was forced to watch the dying minutes of his side's desperate five-point win over Melbourne on Sunday from the bench.

Petrie had been sent off late in the final term under the blood rule and could not return to the field because the Roos had already hit their cap limit of 90 interchanges.

"We'd had 90 interchanges and then we had a blood rule and that blood rule was to a pretty important player in Petrie," Scott said.

"The problem was we couldn't put Drew back on because we'd exceeded the interchange cap.

"When you've got a game as tight as that you're looking at tiny little things like that that can cost you.

"It's a long bow to draw, but theoretically you could have a player removed from the ground under the blood rule in pretty ordinary circumstances and then you can't replace him because you've hit your cap.

"It's not a confusing issue. The AFL have spelled it out pretty clearly but I don't think it's right. You should be able to put the player you've lost to the blood rule back on.

"You'd hate to see it cost someone a game."

Scott was happy but not entirely satisfied following his side's nail-biting win that set a new record high score for an AFL match in Tasmania.

Scott likened his side to a misfiring golfer and suggested they'd only just done enough to win a match the Demons had dominated in several key areas.

"We got the job done," he said.

"I use the analogy the players are the golfer who chops it all over the place but manages to shoot two or three-under par and wins the tournament. No one looks back and recounts every shot and we don't look back and recount every poor decision, every poor kick.

"In 12 weeks' time we'll look back and see a 'W' in the win-loss column."

Having raced to a six-goal lead on the back of a strong breeze blowing in their favour during the first quarter, the Kangaroos could only watch as Melbourne gained full control of the game in the second term and piled on nine goals to take a narrow and unlikely lead into the main break.

Scott admitted his players had been outworked in the contest during the second term by a Melbourne side featuring a potent mix of experienced campaigners and talented youth.

"They outplayed us around the ball," he said. "They've recruited some really good, hard midfielders and I thought on balance they convincingly beat us in the contest throughout the day."

After half-time the game settled into a compelling, end-to-end contest and Scott singled out hard-nosed midfielder Jack Ziebell among others who showed desperation late as the Kangaroos clung on to win.

"It was only some fantastic defensive efforts, Ziebell's 19 tackles, particularly some tackles late, some desperate acts to get us across the line," he said.