THE AFL will consider tweaking the interchange cap rules to accommodate a player forced from the field under the blood rule after a team has reached 90 bench rotations.

North Melbourne coach Brad Scott raised the issue after the Kangaroos defeated Melbourne by five points in a thriller in Hobart on Sunday, after his key forward Drew Petrie was stranded on the bench in the dying seconds.

Petrie had been forced to leave the ground with less than a minute remaining through the blood rule and was replaced by teammate Ben Brown, but he could not return because the Kangaroos had already reached the 90 rotations limit before he left the ground.

Under the rules clubs can replace a player who leaves the ground under the blood rule without incurring a rotation but when that player returns to the ground it counts as a rotation regardless of which player he replaces.

If Petrie had returned to the ground, the Kangaroos would have exceeded the cap and had a free kick paid against them. 

Scott acknowledged it was a rare situation that even his coaches' box had not considered before it occurred but he said it should be addressed.

"It's not a confusing issue. The AFL has 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," Scott said.

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

The AFL is understood to be considering whether clubs should keep one rotation in reserve in the dying minute in case they were faced with the same situation as North Melbourne were on Sunday, or whether a player who leaves the ground due to the blood rule can return as long as he replaces the player who originally replaced him without a rotation being counted as part of the cap.

The AFL will also have to consider how such a rule is policed.

It is possible a decision will be made before round four kicks off.

The interchange cap of 90 was introduced at the start of the season and the substitute was removed with teams now able to use four players on the bench.