THIS IS the best start to a season for Brisbane in 15 years, but it's time the warning bell was sounded for the Lions' leaky defence.

Brisbane has been one of the AFL's feel-good stories of 2019, deservedly racing to a 5-2 record, highlighted by swift ball movement and an exciting collection of talent across every line.

However, there's plenty of room to improve.

On Saturday night against Sydney the Lions had almost twice the inside 50s of the Swans (77-40) but struggled to put the game away due to a combination of poor goalkicking and conceding goals too easily.

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Statistics show not only have Brisbane conceded the fourth-most points in the competition, but just as worryingly, once the ball goes inside their defensive 50, they're one of the easiest teams to score against.

A simple formula to devise how many points are conceded per inside 50 shows the Lions trail only struggling Melbourne and North Melbourne.

The problem is not catastrophic, and the seven-game sample is still a small one, but it's a case of "watch this space" for the Lions.

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A large portion of the damage came in heavy losses to Essendon (112 points from 57 entries) and Collingwood (123 from 62), but they're not isolated examples.

Coach Chris Fagan has highlighted his team's occasional rushed ball movement that leads to turnovers and exposes a scattered defence.

It's part of learning the balance between moving with speed to advantage and moving with structure to counter mistakes.

Small and medium-sized forwards are causing the problems, which is not surprising with Harris Andrews, Darcy Gardiner and revitalised Josh Walker, who was surprisingly dropped this week, locking down the key posts.

In round three it was Port Adelaide whiz-kid Connor Rozee kicking five goals.

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Seven days later Anthony McDonald-Tipungwuti bagged seven for the Bombers, and against Sydney Tom Papley bobbed up with four.

Brisbane is trying to unearth small defenders and used Zac Bailey for the first three weeks before the speedster hurt his hamstring late in the win over Port Adelaide.

Alex Witherden is still young (20 and having played just 37 games), and could develop into that player, but at the moment his strengths lie with ball in hand.

Noah Answerth has now played two games and despite the odd lapse in concentration, shows toughness, sufficient speed and an ability to lock down.

That search for the right defensive mix continues, but as long as Brisbane keeps the big picture in mind, any short-term pain is nothing to panic over.

In the past two off-seasons Brisbane has added Luke Hodge, Charlie Cameron, Lachie Neale, Jarryd Lyons, Lincoln McCarthy and Marcus Adams as it supplements a list full of high-end talent aged 22 and below.

It wouldn't be a shock if they canvassed the market for a lockdown small defender in the coming months.

Until then, keep an eye on the development of the Lions' own talent in that part of the ground and just how proficient they are at stopping opponents scoring from inside 50 entries.