BRISBANE coach Chris Fagan will seek clarity from the League after Logan Morris had a goal wiped away following the three-quarter time siren on Thursday night.

Morris took a mark 30m from goal just before the siren sounded and stepped back off his line to take his set shot as a right foot snap.

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Appearing to kick the ball over the man on the mark, the adjudicating umpire thought otherwise and called play-on, wiping away the goal after the ball sailed between the posts.

Speaking post-match, Fagan said he was confused.

"My understanding of that rule is as long as you start near the boundary and kick over the guy's hands on the mark, that's ok," he said.

"I thought that's what he did. I wasn't standing right there on the spot, but that's what it looked like to me.

"It would be good to get some clarity on it because the learning for Logan might be 'If you ever get another shot on goal and the siren's gone mate, maybe you've just got to go straight back and kick over the hands on the mark so there's no doubt you've done the right thing'.

"From what the explanation is we got earlier in the year, I think he did everything right. What did you guys think?

"We'll ask because he did that thinking he was doing the right thing.

"If he wasn't, we all need to know so we can learn from it. That's ok."

It was reminiscent of Nick Watson's after-the-siren shot against St Kilda in round 12 where the Hawthorn small forward appeared to arc to his right, making his angle worse, having his accurate kick rubbed out.

In the end Morris' misfortune made little difference to Brisbane's night as the two-time premiers trounced the Swans by 43 points with an emphatic display.

The win moved them to sixth place and was arguably their best performance of the season.

Fagan said he was thrilled with the defensive intensity.

"Our big focus tonight was to run forward at them because they want to play that handball game," he said.

"It's a little bit nerve wracking for your players to do that, but that is how you've got to play against them and you've got to take that risk.

"I thought we did that well enough, often enough to create scoring opportunities back the other way.

"It seems to me we just play better defensively when we go hard on attack and just back ourselves in. 

"I think that's the mindset we'll try to play with for the remainder of the year."

Sydney coach Dean Cox said his team got a reminder of the level they needed to reach against the best teams in the competition.

"Brisbane were cleaner, tougher, hungrier," he said. "Plain and simple.

"You can't just rely on one phase of your game to get going.

"That's what you always get, opportunities to learn and level out where you're at and we've always held Brisbane in the highest regard and they showed why."

Sydney left too much to too few, with Chad Warner's scintillating four-goal, 28-disposal game going to waste, while Charlie Curnow was a constant threat inside 50 with three goals.

"The great thing Charlie did was compete," he said.

"The competitive part is the part I like the most.

"Against a backline that Brisbane have, you have to do that, to earn everything you get and we just didn't have enough … of them in our team that wanted to go to the line long enough."