THE AFL may introduce a 'common sense' rule to avoid a repeat of Eddie Betts' disallowed goal in the NAB Challenge.

The umpires have been deemed correct in their play-on decision after the Adelaide Crow's shot for goal hit the goal umpire and bounced back into play during Sunday's pre-season game against North Melbourne.

The kick would have been a goal had it not hit the umpire, and bemused the Crows players who were involved in the passage of play, including Betts himself.

Umpires director Wayne Campbell told AFL.com.au's show First Bounce the umpires had reviewed the incident with football operations boss Mark Evans and conceded a change could be imminent.

"They got the ruling correct. Technically it was correct and they handled it well other than obviously the goal umpire being in the wrong position," Campbell.

"We've had a look at it and I think Mark Evans' approach is common sense along the way - clearly football needs that to be a goal, so we'll have a look at that."

A quirk of the rule means if the ball had hit the umpire and continued through for a goal, it would have been paid the full six points. But the fact it bounced back into play means it was the right decision to call play-on.

Campbell said it would require a rule change – approved by the AFL Commission – to get the right result.   

"That needs to go to [the AFL] Commission so whether we need to do that straight away or not [will need to be decided], but certainly we're reviewing it as we speak," he said.

The AFL last week started its trial of four umpires in games, and will do so again in four games this weekend before reverting to three umpires for the remainder of the pre-season competition.

"It's very much a trial," Campbell said.

"We think it was a success. We want to get our decisional accuracy better, and … they certainly got themselves in better spots.

"We were concerned [that] the GPS says they ran the same distance. We don't want that. We want them running less distances so they can umpire longer and get into better positions.

"We certainly thought there were a couple of free kicks in each game that were paid that we probably would have missed if there hadn't have been the fourth umpire there."

Below: A screen grab shows Eddie Betts tumbling as the ball cannons into the goal umpire.